Composite cathodes, electrochemical cells comprising novel composite cathodes, and processes for fabricating same

ABSTRACT

The present invention pertains to composite cathodes suitable for use in an electrochemical cell, said cathodes comprising: (a) an electroactive sulfur-containing cathode material, wherein said electroactive sulfur-containing cathode material, in its oxidized state, comprises a polysulfide moiety of the formula —S m —, wherein m is an integer equal to or greater than 3; and, (b) an electroactive transition metal chalcogenide composition, which encapsulates said electroactive sulfur-containing cathode material, and which retards the transport of anionic reduction products of said electroactive sulfur-containing cathode material, said electroactive transition metal chalcogenide composition comprising an electroactive transition metal chalcogenide having the formula M j Y k (OR) l  wherein: M is a transition metal; Y is the same or different at each occurrence and is oxygen, sulfur, or selenium; R is an organic group and is the same or different at each occurrence; j is an integer ranging from 1 to 12; k is a number ranging from 0 to 72; and l is a number ranging from 0 to 72; with the proviso that k and l cannot both be 0. The present invention also pertains to methods of making such composite cathodes, cells comprising such composite cathodes, and methods of making such cells.

RELATED APPLICATIONS

This application is a continuation of and claims priority to U.S. patentapplication Ser. No. 10/957,539, filed Oct. 1, 2004, now abandoned whichis a continuation of U.S. patent application Ser. No. 09/795,915, filedFeb. 27, 2001, which is a continuation of U.S. patent application Ser.No. 09/293,498, filed Apr. 15, 1999, now U.S. Pat. No. 6,238,821, whichis a continuation of U.S. patent application Ser. No. 08/859,996, filedMay 21, 1997, now U.S. Pat. No. 5,919,587, which claims priority to U.S.Provisional Patent Application No. 60/018,115, filed 22 May 1996, thecontents of each of which is incorporated herein by reference in theirentirety.

TECHNICAL FIELD

The present invention pertains generally to the field of cathodes andrechargeable electric current producing cells. More particularly, thepresent invention pertains to composite cathodes which comprise (a) anelectroactive sulfur-containing cathode material, wherein saidelectroactive sulfur-containing cathode material, in its oxidized state,comprises a polysulfide moiety of the formula —S_(m)—, wherein m is aninteger equal to or greater than 3; and, (b) an electroactive transitionmetal chalcogenide composition, which encapsulates said electroactivesulfur-containing cathode material, and which retards the transport ofanionic reduction products of said electroactive sulfur-containingcathode material. The present invention also pertains to methods ofmaking such composite cathodes, cells comprising such compositecathodes, and methods of making such cells.

BACKGROUND

Throughout this application, various publications, patents, andpublished patent applications are referred to by an identifyingcitation. The disclosures of the publications, patents, and publishedpatent specifications referenced in this application are herebyincorporated by reference into the present disclosure to more fullydescribe the state of the art to which this invention pertains.

As the evolution of batteries continues, and particularly as lithiumbatteries become more widely accepted for a variety of uses, the needfor safe, long lasting high energy batteries becomes more important.There has been considerable interest in recent years in developing highenergy density cathode-active materials and alkali-metals as anodematerials for high energy primary and secondary batteries. Several typesof cathode materials for the manufacture of thin film lithium and sodiumbatteries are known in the art. The most widely investigated group aremetallic or inorganic materials which include transition metalchalcogenides, such as titanium disulfide with alkali-metals as theanode as described in U.S. Pat. No. 4,009,052. Also among the cathodeactive chalcogenides, U.S. Pat. No. 4,049,879 lists transition metalphosphorous chalcogenides, and U.S. Pat. No. 3,992,222 describes cellsusing mixtures of FeS2 and various metal sulfides as the electroactivecathode materials. U.S. Pat. No. 3,639,174 describes primary andsecondary voltaic cells utilizing lithium aluminum alloy anodes and areversible cathode depolarizer such as cupric sulfide, cuprous oxide,cupric carbonate, and the like that have low solubility in theelectrolyte. U.S. Pat. No. 4,576,697 describes electroactive cathodematerials in alkali-metal non-aqueous secondary batteries comprised ofcarbon-containing intercalatable layered or lamellar transition metalchalcogenides having the general formula MnX2C, wherein M is atransition metal selected from the group consisting of Ti, V, Cr, Fe,Zr, and Ta; X is sulfur; and n is 1-2. High energy density solid statecells comprising cathodes using selected ionically and electronicallyconductive transition metal chalcogenides in combination with othernon-conductive electroactive cathode materials are described in U.S.Pat. No. 4,258,109.

Another type of cathode materials disclosed for use in lithium andsodium batteries are organic materials such as conductive polymers. Afurther type of organic type cathode materials are those comprised ofelemental sulfur, organo-sulfur and carbon-sulfur compositions wherehigh energy density is achieved from the reversible electrochemistry ofthe sulfur moiety with the alkali metal. U.S. Pat. No. 4,143,214 toChang et al. describes cells having cathodes containing C_(v)S wherein vis a numerical value from about 4 to about 50. U.S. Pat. No. 4,152,491to Chang et al. relates to electric current producing cells where thecathode-active materials include one or more polymer compounds having aplurality of carbon monosulfide units. The carbon monosulfide unit isgenerally described as (CS)_(w), wherein w is an integer of at least 5,and may be at least 50, and is preferably at least 100.

U.S. Pat. No. 4,664,991 to Perichaud et al. describes an organo-sulfurmaterial containing a one-dimensional electric conducting polymer and atleast one polysulfurated chain forming a charge-transfer complex withthe polymer. Perichaud et al. use a material which has two components.One is the conducting or conductive polymer, which is selected from agroup consisting of polyacetylenes, polyparaphenylenes, polythiophenes,polypyrroles, polyanilines and their substituted derivatives. The otheris a polysulfurated chain which is in a charge transfer relation to theconducting polymer. The polysulfurated chain is formed by hightemperature heating of sulfur with the conductive polymer to formappended chains of . . . —S—S—S—S— . . . of indeterminate length.

In a related approach, a PCT application (PCT/FR84/00202) of Armand etal. describes derivatives of polyacetylene-co-polysulfurs comprisingunits of Z_(q)(CS_(r))_(n) wherein Z is hydrogen, alkali-metal, ortransition metal, q has values ranging from 0 to values equal to thevalence of the metal ion used, values for r range from greater than 0 toless than or equal to 1, and n is unspecified. These derivatives aremade from the reduction of polytetrafluoroethylene orpolytrifluorochloroethylene with alkali-metals in the presence ofsulfur, or by the sulfuration of polyacetylene with vapors of sulfurmonochloride at 220° C.

U.S. Pat. No. 5,441,831 relates to an electric current producing cellwhich comprises a cathode containing one or more carbon-sulfur compoundsof the formula (CS_(x))_(n), in which x takes values from 1.2 to 2.3 andn is equal to or greater than 2.

U.S. Pat. Nos. 4,833,048 and 4,917,974 to De Jonghe et al. describe aclass of cathode materials made of organo-sulfur compounds of theformula (R(S)_(y))_(n) where y=1 to 6; n=2 to 20, and R is one or moredifferent aliphatic or aromatic organic moieties having one to twentycarbon atoms. One or more oxygen, sulfur, nitrogen or fluorine atomsassociated with the chain can also be included when R is an aliphaticchain. The aliphatic chain may be linear or branched, saturated orunsaturated. The aliphatic chain or the aromatic rings may havesubstituent groups. The preferred form of the cathode material is asimple dimer or (RS)₂. When the organic moiety R is a straight or abranched aliphatic chain, such moieties as alkyl, alkenyl, alkynyl,alkoxyalkyl, alkythioalkyl, or aminoalkyl groups and their fluorinederivatives may be included. When the organic moiety comprises anaromatic group, the group may comprise an aryl, arylalkyl or alkylarylgroup, including fluorine substituted derivatives, and the ring may alsocontain one or more nitrogen, sulfur, or oxygen heteroatoms as well.

In the cell developed by De Jonghe et al. the main cathode reactionduring discharge of the battery is the breaking and reforming ofdisulfide bonds. The breaking of a disulfide bond is associated with theformation of an RS⁻M⁺ ionic complex. The organo-sulfur materialsinvestigated by De Jonghe et al. undergo polymerization (dimerization)and de-polymerization (disulfide cleavage) upon the formation andbreaking of the disulfide bonds. The de-polymerization which occursduring the discharging of the cell results in lower molecular weightpolymeric and monomeric species, namely soluble anionic organicsulfides, which can dissolve into the electrolyte and causeself-discharge as well as reduced capacity, thereby severely reducingthe utility of the organo-sulfur material as cathode-active material andeventually leading to complete cell failure. The result is anunsatisfactory cycle life having a maximum of about 200 deepdischarge-charge cycles, more typically less than 100 cycles asdescribed in J. Electrochem. Soc., Vol. 138, pp. 1891-1895 (1991).

A significant drawback with cells containing cathodes comprisingelemental sulfur, organosulfur and carbon-sulfur materials relates tothe dissolution and excessive out-diffusion of soluble sulfides,polysulfides, organo-sulfides, carbon-sulfides and/orcarbon-polysulfides, hereinafter referred to as anionic reductionproducts, from the cathode into the rest of the cell. This process leadsto several problems: high self-discharge rates, loss of cathodecapacity, corrosion of current collectors and electrical leads leadingto loss of electrical contact to active cell components, fouling of theanode surface giving rise to malfunction of the anode, and clogging ofthe pores in the cell membrane separator which leads to loss of iontransport and large increases in internal resistance in the cell.

Composite cathodes containing an electroactive transition metalchalcogenide have been described, typically as a random agglomeration ordistribution of the electroactive materials, polymers, conductivefillers, and other solid materials in the cathode layer. In an exceptionto these homogeneous composite cathodes, U.S. Pat. Nos. 4,576,883,4,720,910, and 4,808,496 disclose composite cathodes comprising spheresof an electroactive transition metal chalcogenide, such as vanadiumpentoxide, encapsulated as a core material in a polymeric shellcontaining a polymer, an inorganic salt, such as a lithium salt, andoptionally, a conductive carbon. These spheres are prepared by anemulsifying or a spray drying process. However, no mention is made inthese references of encapsulation by transition metal chalcogenides, ofany retarding of the transport of reduced species, of any use withelemental sulfur or sulfur-containing electroactive organic materials,or of any shape of the combined materials other than spheres.

U.S. Pat. No. 3,791,867 to Broadhead et al. describes cells containingcathodes consisting of elemental sulfur as the electroactive materialpresent in a layered structure of a transition metal chalcogenide. Thispatent is directed at preventing the solubilization and transport of theelemental sulfur electroactive material by the electrolyte solvent. Ithas no mention of the formation of soluble reduced species of theelectroactive material, such as soluble sulfides, or of the retarding orcontrol by any means of the transport of these soluble reduced speciesinto the electrolyte layer and other parts of the cell. The transitionmetal chalcogenides in this patent are limited to sulfides and selenidesand do not include transition metal oxides. They are present either as atotally separate layer from the sulfur layer or pressed together withsulfur, in powder form, to provide the composite cathode. There is nomention of any organo-sulfur materials, carbon-sulfur materials, orpolymeric binders in the composite cathode. Also there is no mention ofimproved capacity and battery cycle stability and life by the use of anelectroactive transition metal chalcogenide with the elemental sulfurelectroactive material.

U.S. Pat. No. 5,324,599 to Oyama et al. discloses composite cathodescontaining disulfide organo-sulfur or polyorgano-disulfide materials, asdisclosed in U.S. Pat. No. 4,833,048, by a combination with or achemical derivative with a conductive polymer. The conductive polymersare described as capable of having a porous fibril structure and holdingdisulfide compounds in their pores. Japanese patent publication numberKokai 08-203530 to Tonomura describes the optional addition ofelectroactive metal oxide, such as vanadium oxide, to a compositecathode containing disulfide organo-sulfur materials and polyaniline asthe conductive polymer. Japanese patent publication number Kokai08-124570 describes a layered cathode with alternative layers of organodisulfide compound, electroactive metal oxide and conductive polymerwith layers of mainly conductive polymers.

In a similar approach to overcome the dissolution problem withpolyorgano-disulfide materials by a combination or a chemical derivativewith a conductive, electroactive material, U.S. Pat. No. 5,516,598 toVisco et al. discloses composite cathodes comprising metal-organosulfurcharge transfer materials with one or more metal-sulfur bonds, whereinthe oxidation state of the metal is changed in charging and dischargingthe positive electrode or cathode. The metal ion provides highelectrical conductivity to the material, although it significantlylowers the cathode energy density and capacity per unit weight of thepolyorgano-disulfide material. This reduced energy density is adisadvantage of derivatives of organo-sulfur materials when utilized toovercome the dissolution problem. The polyorganosulfide material isincorporated in the cathode as a metallic-organosulfur derivativematerial, similar to the conductive polymer-organosulfur derivative ofU.S. Pat. No. 5,324,599, and presumably the residual chemical bonding ofthe metal to sulfur within the polymeric material prevents the formationof highly soluble sulfide or thiolate anion species. However, there isno mention in these references of retarding of the transport of actualsoluble reduced sulfide or thiolate anion species formed during chargingor discharging of the cathode. Also, there is no mention in thesereferences of the utility of transition metal chalcogenides, includingoxides, in solving the dissolution problem with polyorganodisulfidematerials. Instead, the transition metal chalcogenides are mentioned asspecifically restricted to their known art of electroactive cathodeinsertion materials with lithium ions, with no utility withpolyorgano-disulfide materials, and with significantly less electricalconductivity than the charge-transfer materials described in thesereferences.

Despite the various approaches proposed for the fabrication of highenergy density rechargeable cells containing elemental sulfur,organo-sulfur and carbon-sulfur cathode materials, or derivatives andcombinations thereof, there remains a need for materials and celldesigns that retard the out-diffusion of anionic reduction products,from the cathode compartments into other components in these cells,improve the utilization of electroactive cathode materials and the cellefficiencies, and provide rechargeable cells with high capacities overmany cycles.

It is therefore an object of the present invention to provide compositecathodes containing high loadings of electroactive sulfur-containingcathode material that exhibit a high utilization of the availableelectrochemical energy and retain this energy capacity withoutsignificant loss over many charge-discharge cycles.

It is another object of the present invention to provide compositecathodes, composite cathode materials, and composite cathode designs,for use in rechargeable cells which allow for highly selective transportof alkali-metal ions into and out of the sulfur-containing cathodeswhile retarding the out-diffusion of anionic reduction products from thecathodes into the cells.

It is a further object of this invention to provide convenient methodsfor fabricating such composite cathodes.

It is yet a further objective of this invention to provide energystoring rechargeable battery cells which incorporate such compositecathodes, and which exhibit much improved self-dischargecharacteristics, long shelf life, improved capacity, and highmanufacturing reliability.

SUMMARY OF THE INVENTION

One aspect of the present invention pertains to a composite cathode foruse in an electrochemical cell, said cathode comprising:

(a) an electroactive sulfur-containing cathode material, wherein saidelectroactive sulfur-containing cathode material, in its oxidized state,comprises a polysulfide moiety of the formula —S_(m)—, wherein m is aninteger equal to or greater than 3; and,

(b) an electroactive transition metal chalcogenide composition, whichencapsulates said electroactive sulfur-containing cathode material, andwhich retards the transport of anionic reduction products of saidelectroactive sulfur-containing cathode material, said electroactivetransition metal chalcogenide composition comprising an electroactivetransition metal chalcogenide having the formula M_(j)Y_(k)(OR)_(l)wherein: M is a transition metal; Y is the same or different at eachoccurrence and is oxygen, sulfur, or selenium; R is an organic group andis the same or different at each occurrence; j is an integer rangingfrom 1 to 12; k is a number ranging from 0 to 72; and l is a numberranging from 0 to 72; with the proviso that k and l cannot both be 0. Inone embodiment, j is an integer ranging from 1 to 6; k is a numberranging from 0 to 13; and, l is a number ranging from 0 to 18.

In one embodiment, the transition metal of said electroactive transitionmetal chalcogenide is selected from the group consisting of: Ti, V, Cr,Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Ru, Rh, Pd, Hf, Ta, W, Re, Os, andIr.

In one embodiment, the electroactive transition metal chalcogenide isselected from the group consisting of: TiS₂, Cr₂S₃, MoS₂, MoSe₂, MnS₂,NbS₂, VS₂, V₂S₅, WS₂, and V₂O₃S₃.

In one embodiment, Y is oxygen. In one embodiment, the electroactivetransition metal chalcogenide is selected from the group consisting of:MoO₂, MnO2, NbO₅, V₂O₅, WO₃, MoO₃, Ta₂O₅, V₂O_(4.5)(OCH(CH₃)₂)_(0.5),and V₂O_(4.5).

In one embodiment, wherein l is greater than 0, said organic group isselected from the group consisting of: alkyl, aryl, arylalkyl, alkanone,alkanol, and alkoxy groups, each containing 1 to 18 carbons. In oneembodiment, wherein l is greater than 0, said organic group is selectedfrom the group consisting of: methyl, ethyl, propyl, isopropyl, butyl,isobutyl, tertiary butyl, pentyl, isopentyl, hexyl, octyl, ethylhexyl,isooctyl, dodecyl, cyclohexyl, decahydronaphthyl, phenyl, methylphenyl,ethylphenyl, hexylphenyl, dodecylphenyl, isopropylphenyl, benzyl,phenylethyl, naphthyl, acetyl, and acetoacetylonate.

In one embodiment, M is selected from the group consisting of V, Nb, Cr,Mo, Mn, W, and Ta; Y is oxygen; R is selected from the group consistingof: ethyl, isopropyl, butyl, acetyl, and acetylacetonate; j is a numberranging from 1 to less than 7; k is a number ranging from 1 to less than14; and, l is equal to or less than about 1.5.

In one embodiment, the transition metal of said electroactive transitionmetal chalcogenide is V. In one embodiment, the transition metal of saidelectroactive transition metal chalcogenide is V and Y is oxygen. In oneembodiment, the electroactive transition metal chalcogenide is avanadium oxide. In one embodiment, the electroactive transition metalchalcogenide composition comprises an aerogel comprising a vanadiumoxide or a xerogel comprising a vanadium oxide. In one embodiment, theelectroactive transition metal chalcogenide is V₂O₅. In one embodiment,the electroactive transition metal chalcogenide is a vanadium alkoxide.In one embodiment, the electroactive transition metal chalcogenide is avanadium oxide isopropoxide.

In one embodiment, the electroactive transition metal chalcogenide ispresent in said composite cathode in the amount of from 2 to 70 weight%. In one embodiment, the electroactive transition metal chalcogenide ispresent in said composite cathode in the amount of from 5 to 50 weight%. In one embodiment, the electroactive transition metal chalcogenide ispresent in said composite cathode in the amount of from 5 to 40 weight%.

In one embodiment, the electroactive transition metal chalcogenidecomposition comprises an aerogel or a xerogel comprising anelectroactive transition metal chalcogenide. In one embodiment, theelectroactive transition metal chalcogenide composition encapsulatessaid electroactive sulfur-containing cathode material by impregnation ofsaid electroactive sulfur-containing cathode material into saidelectroactive transition metal chalcogenide composition. In oneembodiment, the electroactive transition metal chalcogenide compositionis present as an interface layer on the outer surface of saidelectroactive sulfur-containing cathode material. In one embodiment, thecomposite cathode comprises: (a) a first coating on an electricallyconductive substrate, said first coating comprising said electroactivesulfur-containing cathode material; and, (b) a second coating over saidfirst coating, said second coating comprising said electroactivetransition metal chalcogenide composition. In one embodiment, the secondcoating comprises greater than 2.5g/m² of said electroactive transitionmetal chalcogenide.

In one embodiment, the sulfur-containing material comprises elementalsulfur.

In one embodiment, the sulfur-containing material comprises acarbon-sulfur polymer material. In one embodiment, the sulfur-containingmaterial is a carbon-sulfur polymer material, wherein m of thepolysulfide moiety, —S_(m)—, of said carbon-sulfur polymer material isan integer equal to or greater than 6. In one embodiment, the polymerbackbone chain of said carbon-sulfur polymer material comprisesconjugated segments. In one embodiment, the polysulfide moiety, —S_(m)—,is covalently bonded by one or both of its terminal sulfur atoms on aside group to the polymer backbone chain of said carbon-sulfur polymermaterial. In one embodiment, the polysulfide moiety, —S_(m)—, isincorporated into the polymer backbone chain of said carbon-sulfurpolymer material by covalent bonding of said polysulfide moiety'sterminal sulfur atoms.

In one embodiment, the carbon-sulfur polymer material comprises greaterthan 75 weight percent of sulfur.

In one embodiment, the composite cathode further comprises one or moreof the materials selected from the group consisting of: binders,electrolytes, and conductive additives. In one embodiment, the compositecathode further comprises one or more binders selected from the groupconsisting of: polytetrafluoroethylenes, polyvinylidene fluorides,ethylene propylene diene (EPDM) rubbers, polyethylene oxides, UV curableacrylates, UV curable methacrylates, and UV curable divinyl ethers. Inone embodiment, the composite cathode further comprises one or moreconductive additives selected from the group consisting of: conductivecarbons, graphites, metal flakes, metal powders, and conductivepolymers.

Another aspect of the present invention pertains to methods forpreparing a composite cathode, as described herein, for use in anelectrochemical cell.

In one embodiment, said methods comprise the steps of:

(a) dissolving or dispersing the electroactive transition metalchalcogenide in a liquid medium;

(b) adding to the composition resulting from step (a) the electroactivesulfur-containing cathode material;

(c) mixing the composition resulting from step (b) to dissolve ordisperse said electroactive sulfur-containing cathode material, therebyforming a composition having a desired consistency and particle sizedistribution;

(d) casting the composition resulting from step (c) onto a suitablesubstrate or placing the composition resulting from step (c) into amold;

(e) removing some or all of the liquid from the composition resultingfrom step (d) to provide a solid or gel-like composite cathode structurein the shape or form desired; and

(f) optionally heating the composite cathode structure of step (e) to atemperature of 100° C. or greater.

In one embodiment, said methods comprise the steps of:

(a) dissolving or dispersing the electroactive transition metalchalcogenide in a liquid medium;

(b) adding to the composition resulting from step (a) the electroactivesulfur-containing cathode material;

(c) mixing the composition resulting from step (b) to dissolve ordisperse said electroactive sulfur-containing cathode material, therebyforming a composition having a desired consistency and particle sizedistribution;

(d) contacting the composition resulting from step (c) with a gellingagent, thereby forming a sol-gel having a desired viscosity;

(e) casting the composition resulting from step (d) onto a suitablesubstrate or placing the composition resulting from step (d) into amold;

(f) removing some or all of the liquid from the composition resultingfrom step (e) to provide a solid or gel-like composite cathode structurein the shape or form desired; and

(g) optionally heating the composite cathode structure of step (f) to atemperature of 100° C. or greater.

In one embodiment, said methods comprise the steps of:

(a) dissolving the electroactive transition metal chalcogenide (e.g.,electroactive transition metal alkoxide or electroactive transitionmetal chalcogenide precursor) in a liquid medium;

(b) contacting the composition resulting from step (a) with a gellingagent, thereby forming a sol-gel having a desired viscosity;

(c) adding to the composition resulting from step (b) the electroactivesulfur-containing cathode material;

(d) mixing the composition resulting from step (c) to dissolve ordisperse said electroactive sulfur-containing cathode material, therebyforming a composition having a desired consistency and particle sizedistribution;

(e) casting the composition resulting from step (d) onto a suitablesubstrate or placing the composition resulting from step (d) into amold;

(f) removing some or all of the liquid from the composition resultingfrom step (e) to provide a solid or gel-like composite cathode structurein the shape or form desired; and

(g) optionally heating the composite cathode structure of step (f) to atemperature of 100° C. or greater.

In one embodiment, said methods comprise the steps of:

(a) coating a current collector substrate with a composition comprisingthe electroactive sulfur-containing cathode material and drying orcuring said composition to form a solid or gel-type electroactivecathode layer on said current collector substrate;

(b) dissolving or dispersing the electroactive transition metalchalcogenide in a liquid medium; and

(c) coating said electroactive cathode layer with the compositionresulting from step (b) and drying or curing said composition to form asolid layer of said electroactive transition metal chalcogenidecomposition which covers the outer surface of said electroactive cathodelayer.

In one embodiment, said methods comprise the steps of:

(a) coating a current collector substrate with a composition comprisingthe electroactive sulfur-containing cathode material and drying orcuring said composition to form a solid or gel-type electroactivecathode layer on said current collector substrate;

(b) dissolving or dispersing the electroactive transition metalchalcogenide in a liquid medium;

(c) contacting the composition resulting from step (b) with a gellingagent, thereby forming a sol-gel having a desired viscosity; and

(d) coating said electroactive cathode layer with the compositionresulting from step (c) and drying or curing said composition to form asolid layer of said electroactive transition metal chalcogenidecomposition which covers the outer surface of said electroactive cathodelayer.

Another aspect of the present invention pertains to electric currentproducing cells comprising (a) an anode; (b) a composite cathode, asdescribed herein; and (c) an electrolyte between said anode and saidcomposite cathode.

In one embodiment, the cell has an increase of specific capacity ofgreater than 150 mAh per gram of said electroactive transition metalchalcogenide, with respect to the specific capacity of saidelectroactive sulfur-containing cathode material. In one embodiment, thecell has an increase of specific capacity of greater than 200 mAh pergram of said electroactive transition metal chalcogenide, with respectto the specific capacity of said electroactive sulfur-containing cathodematerial. In one embodiment, the cell has an increase of specificcapacity of greater than 300 mAh per gram of said electroactivetransition metal chalcogenide, with respect to the specific capacity ofsaid electroactive sulfur-containing cathode material. In oneembodiment, the anode comprises one or more materials selected from thegroup consisting of: lithium metal, lithium-aluminum alloys, lithium-tinalloys, lithium intercalated carbons, lithium intercalated graphites,calcium metal, aluminum metal, sodium metal, and sodium alloys. In oneembodiment, the electrolyte comprises one or more materials selectedfrom the group consisting of: liquid electrolytes, gel polymerelectrolytes, and solid polymer electrolytes. In one embodiment, theelectrolyte comprises: (a) one or more solid polymer electrolytesselected from the group consisting of: polyethers, polyethylene oxides,polyimides, polyphosphazenes, polyacrylonitriles, polysiloxanes,polyether grafted polysiloxanes; derivatives of the foregoing;copolymers of the foregoing; crosslinked and network structures of theforegoing; blends of the foregoing; and (b) one or more ionicelectrolyte salts. In one embodiment, the electrolyte comprises: (a) oneor more materials selected from the group consisting of: polyethyleneoxides, polypropylene oxides, polyacrylonitriles, polysiloxanes,polyimides, polyethers, sulfonated polyimides, perfluorinated membranes(Nafion™ resins), divinyl polyethylene glycols, polyethyleneglycol-bis-(methyl acrylates), polyethylene glycol-bis(methylmethacrylates); derivatives of the foregoing; copolymers of theforegoing; crosslinked and network structures of the foregoing; blendsof the foregoing; (b) one or more gel forming agents selected from thegroup consisting of: ethylene carbonate, propylene carbonate, N-methylacetamide, acetonitrile, sulfolane, polyethylene glycols,1,3-dioxolanes, glymes, siloxanes, and ethylene oxide grafted siloxanes;blends of the foregoing; and (c) one or more ionic electrolyte salts. Inone embodiment, the gel-forming agent is a material of the followingformula:

wherein o is an integer equal to or greater than 1; p is an integerequal to or greater than 0 and less than about 30, and, the ratio t/s isequal to or greater than 0. In one embodiment, the electrolytecomprises: (a) one or more electrolyte solvents selected from the groupconsisting of: ethylene carbonate, propylene carbonate, N-methylacetamide, acetonitrile, sulfolane, polyethylene glycols,1,3-dioxolanes, glymes, siloxanes, and ethylene oxide grafted siloxanes;blends of the foregoing; and (b) one or more ionic electrolyte salts. Inone embodiment, the electrolyte comprises one or more ionic electrolytesalts selected from the group consisting of: MClO₄, MAsF₆, MSO₃CF₃,MSO₃CH₃, MBF₄, MB(Ph)₄,

where M is Li or Na.

Another aspect of the present invention pertains to methods of formingan electric current producing cells comprising the steps of: (a)providing an anode; (b) providing a composite cathode, as describedherein; and (c) enclosing an electrolyte between said anode and saidcomposite cathode.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a composite cathode on a current collector incorporating acathode configuration wherein the electroactive sulfur-containingcathode material is encapsulated with a thin coating of theelectroactive transition metal chalcogenide composition. These“core-shell” electroactive cathode materials are bound together in acomposite cathode optionally using a binder containing a conductiveadditive and/or an electrolyte.

FIG. 2 shows a composite cathode configuration on a current collectorwherein the electroactive transition metal chalcogenide compositionremains as an interface layer at the boundaries of the electroactivesulfur-containing cathode particles.

FIG. 3 shows a cathode design on a current collector wherein a coatingof the electroactive sulfur-containing cathode material is coated orimpregnated with a layer of the electroactive transition metalchalcogenide composition.

FIG. 4 shows a cathode design on a current collector wherein theelectroactive transition metal chalcogenide composition is an aerogel orxerogel and forms a highly porous, fibrous, and ultrafine sponge-likenetwork into which the electroactive sulfur-containing cathode materialsare embedded or encapsulated. The matrix of the transition metalchalcogenide composition may optionally contain binders, electrolytes,and conductive additives.

FIG. 5 shows cyclic voltammograms of a composite cathode of the presentinvention as described in Example 5: (a) initial scan, and (b) secondscan.

FIG. 6 shows discharge curves for a battery cell comprised of thecomposite cathode material described in Examples 3 and 6, a lithiumanode, and an electrolyte of tetraethyleneglycol dimethyl ether (TEGDME)and lithium triflate at 25° C.

FIG. 7 shows charge-discharge curves for a battery cell containing acomposite cathode described in Example 6.

FIG. 8 shows the ultraviolet (UV)-visible absorption spectra of theliquid electrolytes removed from battery cells after cycling: (a)electrolyte from a battery cell comprising a sulfur and carbon cathodewithout an electroactive transition metal chalcogenide composition, and(b) the electrolyte from a similar battery cell containing a compositecathode of the present invention comprising the same sulfur and carbonmaterials and an electroactive V₂O₅ material. Curve (c) shows thespectrum of the electrolyte before cycling.

FIG. 9 is a plot of capacity versus cycle number for a rechargeablebattery cell described in Example 10.

FIG. 10 is a plot of the specific capacity versus cycle number forrechargeable batteries with (●) and without (▪) a surface barriercoating comprising a transition metal chalcogenide composition describedin Example 16.

DETAILED DESCRIPTION OF THE INVENTION

One aspect of the present invention pertains to novel high energydensity composite cathodes comprised of:

(a) an electroactive sulfur-containing cathode material comprising oneor more materials selected from the group consisting of elementalsulfur, organo-sulfur and carbon-sulfur compositions, and derivativesand combinations thereof; and

(b) an electroactive transition metal chalcogenide compositioncomprising one or more electroactive transition metal chalcogenides.

In one embodiment, the present invention pertains to a composite cathodefor use in an electrochemical cell, said cathode comprising:

(a) an electroactive sulfur-containing cathode material, wherein saidelectroactive sulfur-containing cathode material, in its oxidized state,comprises a polysulfide moiety of the formula —S_(m)—, wherein m is aninteger equal to or greater than 3, as described herein; and,

(b) an electroactive transition metal chalcogenide composition, whichencapsulates said electroactive sulfur-containing cathode material, andwhich retards the transport of anionic reduction products of saidelectroactive sulfur-containing cathode material.

The electroactive transition metal chalcogenide facilitates thetransport of alkali-metal and/or alkaline-earth metal cations reversiblyfrom an electrolyte to the electroactive sulfur-containing cathodematerial, and also efficiently retards the transport of anionicreduction products from the composite cathode to the electrolyte orother layers or parts of the cell (e.g., retards the transport ofanionic reduction products of said sulfur-containing material to theoutside of said composite cathode). Thus, the transition metalchalcogenide composition effectively encapsulates or embeds theelectroactive sulfur-containing cathode material and/or effectivelyentraps any soluble sulfide species generated during charging anddischarging of the cell. The composite cathodes of the present inventionthus provide high energy density and low out-diffusion of anionicreduction products.

The composite cathodes of the present invention are particularlypreferred for use in electrolytic cells, rechargeable batteries, fuelcells, and the like that comprise organic type electroactivesulfur-containing cathode components and require high energy storagecapacity, long shelf life, and a low rate of self-discharge.

Electroactive Transition Metal Chalcogenides

The composite cathodes of the present invention comprise anelectroactive transition metal chalcogenide composition comprising oneor more electroactive transition metal chalcogenides of the formulaM_(j)Y_(k)(OR)_(l), wherein:

M is a transition metal;

Y is the same or different at each occurrence and is oxygen, sulfur orselenium;

R is an organic group and is the same or different at each occurrence;

j is an integer ranging from 1 to about 12;

k is a number ranging from 0 to about 72; and

l is a number ranging from 0 to about 72;

with the proviso that k and l cannot both be 0;

wherein said electroactive transition metal chalcogenide compositioneffectively encapsulates or embeds the electroactive sulfur-containingcathode material.

In one embodiment, the electroactive transition metal chalcogenidecomposition consists essentially of an electroactive transition metalchalcogenide. In one embodiment, the electroactive transition metalchalcogenide composition further comprises additives such as binders,fillers, and/or electrolytes, as described herein.

The electroactive transition metal chalcogenide facilitates thetransport of alkali-metal ions and/or alkaline-earth metal ionsreversibly from an electrolyte in an electrolytic cell to theelectroactive sulfur-containing cathode material, and also retards thetransport of anionic reduction products from the composite cathode tothe electrolyte or other layers or parts of the cell. Thus, usefulelectroactive transition metal chalcogenides are those that allow foreither alkali-metal or alkaline-earth metal ion insertion and transport,but which retard or hinder the transport of anionic reduction products.

As used herein, the term “electroactive” material is a material whichtakes part in the electrochemical reaction of charge or discharge. Asused herein, the term “electroactive transition metal chalcogenide” isan electroactive material having a reversible lithium insertion ability,wherein the transition metal is at least one selected from the groupconsisting of Ti, V, Cr, Mn, Fe, Nb, Mo, Ta, W, Co, Ni, Cu, Y, Zr, Ru,Rh, Pd, Hf; Re, Os, and Ir, and the chalcogenide is at least oneselected from the group consisting of O, S, and Se.

Examples of preferred electroactive transition metal chalcogenides foruse in the composite cathodes of the present invention are those ofempirical formula M_(j)Y_(k)(OR)_(l) wherein:

M is a transition metal;

Y is the same or different at each occurrence and is selected from thegroup consisting of oxygen, sulfur, and selenium;

R is an organic group and is the same or different at each occurrenceand is selected from the group of alkyl, aryl, arylalkyl, alkylaryl,alkanone, alkanol, and alkoxy groups each containing 1 to about 18carbons;

j is an integer ranging from 1 to about 12;

k is a number ranging from 0 to about 72; and

l is a number ranging from 0 to about 72;

with the proviso that k and l cannot both be 0.

More examples of preferred electroactive transition metal chalcogenidesare those wherein:

M is selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni,Cu, Y, Zr, Nb, Mo, Ru, Rh, Pd, Hf. Ta, W, Re, Os, and Ir;

Y is the same or different at each occurrence and is selected from thegroup consisting of oxygen and sulfur;

R is the same or different at each occurrence and is selected from thegroup consisting of methyl, ethyl, propyl, isopropyl, butyl, isobutyl,tertiary butyl, pentyl, isopentyl, hexyl, octyl, ethylhexyl, isooctyl,dodecyl, cyclohexyl, decahydronaphthyl, phenyl, methylphenyl,ethylphenyl, hexylphenyl, dodecylphenyl, isopropylphenyl, benzyl,phenylethyl, naphthyl, acetyl, and acetoacetylonate(—CH₂—CO—CH₂—CO—CH₃);

j is an integer ranging from 1 to about 6;

k is a number ranging from 0 to about 13; and

l is a number ranging from 0 to about 18;

with the proviso that k and l cannot both be 0.

Still more examples of preferred electroactive transition metalchalcogenides are those wherein:

M is selected from the group consisting of V, Nb, Cr, Mo, Mn, W, and Ta;

Y is oxygen;

R is selected from the group consisting of ethyl, isopropyl, butyl,acetyl, and acetylacetonate;

j is equal to or greater than 1 and less than 7;

k is equal to or greater than 1 and less than 14; and,

l is equal to or less than about 1.5.

Still more examples of useful electroactive transition metalchalcogenides in the practice of this invention are Cr₂O₃, CrO₃, Cr₃O₈,CrS₂, Cr₂S₃, CoO₂, CoS₂, Co₆S₅, Co₄S₃, CuO, Cu₂O, CuSe, CuS, Ti₂O₃,TiO₂, TiS₂, TiS₃, V₂O₃, VO₂, V₂O₄, V₂O₅, V₃O₈, V₆O₁₃, V₂O_(4.5), V₂O₃S₃,V₂O_(4.5)(OCH(CH₃)₂)_(0.5), V₂S₃, VSe₂, MnS₂, MnO, Mn₂O₃, MnO₂, MnS,Fe₃O₄, Fe₂O₃, FeSe, FeS, FeS₂, NiO₂, NiSe, NiS₂, NiS, Y₂O₃, Y₂S₃, Nb₂,NbO, NbO₂, Nb₂O₅, NbSe₂, NbSe₃, MoO₂, MoO₃, MoSe₂, MoS₂, MoS₃, Rh2O₃,RhO₂, PdO, PdS, HfO₂, Ta₂O₅, TaS₂, WO_(2.9), WO₃, WSe₂, WS₂, ReO₂,Re₂O₇, ReS₂, Re₂S₇, OsO₄, and OsO₂. Also useful are carbon-containingtransition metal chalcogenides as described in U.S. Pat. No. 4,576,697.

Especially preferred are electroactive transition metal chalcogenidesselected from the group consisting of: TiS₂, Cr₂S₃, MoS₂, MoSe₂, MoO₂,MnO₂, MnS₂, Nb₂O₅, NbS₂, VS₂, V₂O₅, V₂S₅, WO₃, WS₂, MoO₃, Ta₂O₅,V₂O_(4.5)(OCH(CH₃)₂)_(0.5), V₂O_(4.5), and V₂O₃S₃

Particularly preferred are electroactive V₂O₅ and vanadium oxides ofother stoichiometry, including vanadium oxysulfides.

Both electrically conductive and electrically non-conductiveelectroactive transition metal chalcogenides are useful in the practiceof this invention. Preferred electroactive transition metalchalcogenides are those that are electrical conductive in addition tobeing ionically conductive. Some transition metal chalcogenides areinherently electrically conductive while others become electricallyconductive upon insertion of alkali-metal or alkaline-earth metalcations. Both types are particularly useful. Without wishing to be boundto any particular theory, it is believed that good electricalconductivity in a transition metal chalcogenide in the compositecathodes of the present invention can provide for a more evendistribution of electric fields within the composite cathode therebyproviding a more even distribution of charge storage in theelectroactive sulfur-containing cathode material in the compositecathode, improving charge and discharge characteristics, and improvingoverall capacity and utilization of the electroactive cathode materials.Additionally, transition metal chalcogenides which are electricallyconductive can eliminate or reduce the need for incorporatingnon-electroactive conductive additives in the composite cathodes of thepresent invention. Especially preferred are electroactive transitionmetal chalcogenide compositions having electrical conductivities betweenabout 10⁻⁵ S/cm and 10⁺³ S/cm (S=Siemens).

Preferred electroactive transition metal chalcogenides for use in thepractice of the present also insert (or intercalate) and transportalkali-metal cations within the voltage range from about +0.1 to about+6 volts versus lithium. Especially preferred are electroactivetransition metal chalcogenides which insert and transport alkali-metalcations within the voltage range of about +1.0 to +4.5 volts versuslithium. Particularly preferred are electroactive transition metalchalcogenides that are electroactive at voltages equal to and greaterthan the onset reduction voltage of the employed electroactivesulfur-containing cathode material in the composite cathode of thepresent invention, and also insert and transport alkali metal cationswithin a voltage range up to +4.5 volts versus lithium.

Also preferred in the practice of this invention are electroactivetransition metal chalcogenides that independently or in combination withthe electroactive sulfur-containing cathode composition provide energystorage capacity to the composite cathode. Preferred are compositionswith additional specific energy storage capacities of greater than about150 mAh/g. Especially preferred are compositions with additional storagecapacities of greater than 200 mAh/g and particularly preferred arethose with additional storage capacities of greater than about 300mAh/g.

Especially preferred are electroactive transition metal chalcogenides,such as vanadium oxides, which may be processed by sol-gel techniques(such as those described below), and aerogel and xerogel processingmethods, as known in the art. Without wishing to be bound to anyparticular theory, it is believed that composite cathodes fabricated bya sol-gel type process additionally provide enhanced adhesion tometallic current-collecting substrates and have good self-adhesionproperties so as to minimize the need for adding binders to thecomposite cathode. It is further believed that the nanoscale porosityprovided in the gels provides nanostructured electroactive transitionmetal chalcogenide materials that act like porous catalytic surfaceswithin the composite cathode. These active nanoscale structureseffectively encapsulate, bind or entrap, the electroactivesulfur-containing cathode materials, as well as effectively bind orcomplex the anionic reduction products produced during discharge of thecells, thereby retarding their diffusion out of the cathode structuresinto the cells. In support of this, the experimental results on the zetapotential of vanadium oxide sol indicate that the sol is cationic innature. Thus, it is expected that, in the cell in the presence of liquidelectrolyte, the corresponding gel particles formed from anelectroactive transition metal chalcogenide sol (e.g., vanadium oxidesol) can prevent or retard the anionic reduction products from beingtransported outside of the composite cathode layer. Further, since theelectroactive transition-metal chalcogenide facilitates reversiblemetal-ion transport, these porous catalytic surfaces may facilitate theredox reactions of the electroactive sulfur-containing cathode materialson their surfaces thereby enhancing both capacity and cycleability ofthe electroactive materials. This is especially true when theelectroactive transition metal chalcogenide composition is inherentlyelectrically conductive in addition to being ionically conductive.Hence, it is believed that the transition metal chalcogenide in thecomposite cathodes of the present invention is highly multifunctional interms of its performance.

Electroactive Sulfur-Containing Cathode Materials

The nature of the electroactive sulfur-containing cathode materialsuseful in the practice of this invention can vary widely. Theelectroactive properties of elemental sulfur and of sulfur-containingorganic materials are well known in the art, and include the reversibleformation of lithiated or lithium ion sulfides during the discharge orcathode reduction cycle of the battery cell.

Examples of electroactive sulfur-containing cathode materials arecarbon-sulfur compositions of general formula C_(v)S, wherein v is anumerical value within the range of about 4 to about 50 as described inU.S. Pat. No. 4,143,214. Other examples of electroactivesulfur-containing cathode materials are those which contain one or morepolymer compounds having a plurality of carbon monosulfide units thatmay generally be written as (CS)_(w), wherein w is an integer of atleast 5, as described in U.S. Pat. No. 4,152,491.

Further examples include those containing one or more carbon-sulfurcompounds of formulae (CS_(x))_(n), (CS₂)_(n), and (C₂S_(z))_(n).Compositions of general formula I,—(CS_(x))_(n)—  I

wherein x takes values from 1.2 to 2.3 and n is an integer equal to orgreater than 2, are described in U.S. Pat. No. 5,441,831. Additionalexamples are those of general formula I wherein x ranges from greaterthan 2.3 to about 50, and n is equal to or greater than 2, as describedin U.S. Pat. No. 5,601,947 and U.S. patent application Ser. No.08/729,713. These materials may optionally incorporate large fractionsof elemental sulfur or polysulfur components, which on electrochemicalreduction in an electrolytic cell, provide exceptionally high storagecapacity per unit weight of material. Other examples ofsulfur-containing compositions in the practice of this invention arematerials of formula (CS₂)_(n) made from carbon disulfide as describedby J. J. Colman and W. C. Trogler in J. Amer. Chem. Soc. 1995, 117,11270-11277. These various carbon-sulfur materials, when used as cathodematerials in battery cells, may be optionally mixed with conductivecomponents, electrolytes, and binders to improve electrochemicalrecycleability and capacity of the electroactive sulfur-containingcathode material.

Materials of formula I can be prepared by the reduction of carbondisulfide with alkali-metals, such as sodium or lithium, in anappropriate solvent such as dimethyl sulfoxide, dimethyl formamide(DMF), N-methyl pyrrolidinone, hexamethyl phosphoramide, and the like,incorporating long reaction times before work-up, as described in theaforementioned U.S. Pat. No. 5,601,947 and U.S. patent application Ser.No. 08/729,713. Reaction times greater than about 41 hours provideelectroactive carbon-sulfur cathode materials with elementalcompositions containing between about 86 wt % and 98 wt % sulfur.Preferred compositions are those that have elemental compositionscontaining between about 90 wt % and 98 wt % sulfur. Although thedetailed structures of the materials made by this method have not beencompletely determined, available structural information suggests thatmaterials of this general formula are comprised of one or more of thestructural units of formulae II-V,

wherein m is the same or different at each occurrence and is greaterthan 2, u is the same or different at each occurrence and is equal to orgreater than 1, and the relative amounts of a, b, c, and d comprisingsaid carbon-sulfur polymer or polycarbon sulfide (PCS) material can varywidely and depend on the method of synthesis. Preferred PCS compositionswith high electrochemical capacity are those containing substantialamounts of polysulfide species —(S_(m))— incorporated in and attached tothe polymer backbone. Especially preferred compositions are thosewherein m is on the average equal to or greater than 6. A key feature ofthese compositions is that the polymer backbone structure containsconjugated segments which may facilitate electron transport duringelectrochemical oxidation and reduction of the polysulfur side groups.

Additional examples of electroactive carbon-sulfur cathode materials arecompositions of general formula VI,—(C₂S_(z))_(n)—  VI

wherein z ranges from greater than 1 to about 100, and n is equal to orgreater than 2, as described in U.S. Pat. No. 5,529,860 and U.S. patentapplication Ser. No. 08/602,323. The material may also comprise largefractions of elemental sulfur and polysulfur components, which onelectrochemical reduction in an electrolytic cell, provide exceptionallyhigh storage capacity per unit weight of material. These carbon-sulfurmaterials when used as cathode materials in battery cells, may beoptionally mixed with conductive components, polymeric binders andelectrolytes to further improve electrochemical recycleability andcapacity of said electroactive cathode material.

Materials of formula VI can be prepared, as described in theaforementioned U.S. Pat. No. 5,529,860 and U.S. patent application Ser.No. 08/602,323, by the reaction of acetylene with a metal amide, such assodium amide or sodium diisopropylamide, and elemental sulfur in asuitable solvent, such as liquid ammonia. Although the detailedstructure of such materials has not been completely determined,available structural information suggests that these compositions arecomprised of one or more of the structural units of formulae IV-V,VII-IX;

wherein m is the same or different at each occurrence and is greaterthan 2; and the relative amounts of c, d, e, f, and g, in said materialscan vary widely and will depend on the method of synthesis. Preferredcompositions are those wherein m is equal to or greater than 3, andespecially preferred compositions are those wherein m is on the averageequal to or greater than 6. These materials typically have elementalcompositions containing between about 50 wt % and 98 wt % sulfur.Preferred compositions are those that have elemental compositionscontaining between about 80 wt % and 98 wt % sulfur.

Additional examples of electroactive sulfur-containing cathode materialsare organo-sulfur substances containing one-dimensional electronconducting polymers and at least one polysulfurated chain forming acomplex with said polymer, as described in U.S. Pat. No. 4,664,991.Other examples of electroactive sulfur-containing cathode materials arethose comprising organo-sulfur compounds of the formula (R(S)_(y))_(n),where y=1 to 6; n=2 to 20, and R is one or more different aliphatic oraromatic organic moieties having one to twenty carbon atoms as describedin U.S. Pat. Nos. 4,833,048 and 4,917,974. Still other examples ofelectroactive sulfur-containing cathode materials are organo-sulfurpolymers with the general formula (R(S)_(y))_(n), as described in U.S.Pat. No. 5,162,175. Yet more examples of organo-sulfur cathode materialsare those comprising a combination of a compound having a disulfidegroup and a conductive polymer, or an organo-disulfide derivative of aconductive polymer, as described in U.S. Pat. No. 5,324,599. Additionalexamples of organo-sulfur materials are the organo-sulfur derivatives ofmetal ions as described in U.S. Pat. No. 5,516,598.

Thus, in a preferred embodiment, composite cathodes of the presentinvention comprise (a) an electroactive sulfur-containing material,wherein said electroactive sulfur-containing material, in its oxidizedstate, comprises a polysulfide moiety of the formula —S_(m)—, wherein mis an integer equal to or greater than 3; and, (b) an electroactivetransition metal chalcogenide composition, as described herein.

In one embodiment, the electroactive sulfur-containing materialcomprises elemental sulfur. In one embodiment, the electroactivesulfur-containing material comprises a carbon-sulfur polymer. In oneembodiment, the electroactive sulfur-containing material comprises acarbon-sulfur polymer and m is an integer equal to or greater than 6. Inone embodiment, the electroactive sulfur-containing material comprises acarbon-sulfur polymer, and the polymer backbone chain of saidcarbon-sulfur polymer comprises conjugated segments. In one embodiment,the electroactive sulfur-containing material comprises a carbon-sulfurpolymer, and the polysulfide moiety, —S_(m)—, is covalently bonded byone or both of its terminal sulfur atoms on a side group to the polymerbackbone chain of said carbon-sulfur polymer material. In oneembodiment, the electroactive sulfur-containing material comprises acarbon-sulfur polymer, and the polysulfide moiety, —S_(m)—, isincorporated into the polymer backbone chain of said carbon-sulfurpolymer by covalent bonding of said polysulfide moiety's terminal sulfuratoms. In one embodiment, the electroactive sulfur-containing materialcomprises a carbon-sulfur polymer comprising more than 75% sulfur byweight.

Quite surprisingly, it was discovered that when elemental sulfur is usedas the electroactive sulfur-containing material in the compositecathodes of the present invention, the sulfur is rendered more highlyelectrochemically active providing very high reversible capacity. Lowself discharge and high cycle life are provided by the effectiveencapsulation or entrapping of the elemental sulfur and retarding ofsulfide out-diffusion by the transition metal chalcogenide compositions.

Composite Cathodes

One aspect of the present invention pertains to a composite cathode foruse in an electrochemical cell, said cathode comprising:

(a) an electroactive sulfur-containing cathode material, wherein saidelectroactive sulfur-containing cathode material, in its oxidized state,comprises a polysulfide moiety of the formula —S_(m)—, wherein m is aninteger equal to or greater than 3, as described herein; and,

(b) an electroactive transition metal chalcogenide composition, whichencapsulates said electroactive sulfur-containing cathode material, andwhich retards the transport of anionic reduction products of saidelectroactive sulfur-containing cathode material, said electroactivetransition metal chalcogenide composition comprising an electroactivetransition metal chalcogenide having the formula:M_(j)Y_(k)(OR)_(l)wherein

M is a transition metal;

Y is the same or different at each occurrence and is oxygen, sulfur, orselenium;

R is an organic group and is the same or different at each occurrence;

j is an integer ranging from 1 to 12;

k is a number ranging from 0 to 72; and

l is a number ranging from 0 to 72;

with the proviso that k and l cannot both be 0; as described herein.

The present invention also pertains to the design and configuration ofcomposite cathodes of the present invention. The relative configurationof the electroactive sulfur-containing cathode material and theelectroactive transition metal chalcogenide composition in the compositecathode is critical. In all cases, in order to retard out-diffusion ofanionic reduction products from the cathode compartment in the cell, thesulfur-containing cathode material must be effectively separated fromthe electrolyte or other layers or parts of the cell by a layer of anelectroactive transition metal chalcogenide composition. Surprisingly,it has been discovered that this layer can be dense or porous.

One design incorporates a fabricated cathode comprising a mixture of theelectroactive sulfur-containing cathode material, the electroactivetransition metal chalcogenide, and optionally binders, electrolytes, andconductive additives, which is deposited onto a current collector.

Another design is one where a coating of the electroactivesulfur-containing cathode material is encapsulated or impregnated by athin coherent film coating of the cation transporting, anionic reductionproduct transport-retarding, transition metal chalcogenide composition.

Yet another design of said composite cathode of the present inventionincorporates a cathode comprised of particulate electroactivesulfur-containing cathode materials individually coated with anencapsulating layer of the cation transporting, anionic reductionproduct transport-retarding, transition metal chalcogenide composition.

In one embodiment of the present invention, the cathode is comprised ofparticulate sulfur-containing cathode materials, generally less than 10μm (microns) in diameter, individually coated with an encapsulatinglayer of an alkali-metal cation-transporting, yet anionic reductionproduct transport-retarding electroactive transition metal chalcogenidecomposition. A cathode fabricated from such a “core-shell” configurationof materials is illustrated in FIG. 1. Here, the prismatic cathodestructure 1 in contact with a current collector 2 is comprised ofcompacted powders of the composite cathode. Each composite cathodeparticle is comprised of a core 3 of the electroactive sulfur-containingcathode material with an outer shell 4 of a retarding barrier layercomprising an electroactive transition metal chalcogenide. Optionally,said composite cathode may contain fillers 5 comprising various types ofbinders, electrolytes and conductive materials that are well known tothose skilled in the art.

Another embodiment of the present invention is shown in FIG. 2, whichillustrates a prismatic composite cathode structure 1 in contact with acurrent collector 2 and comprising electroactive sulfur-containingcathode particles 6 as a dispersed phase in a matrix consisting of anelectroactive transition metal chalcogenide phase 7 that optionallycontains a binder, an electrolyte, and a conductive filler. Theelectroactive transition metal chalcogenide phase facilitates the highlyselective and reversible transport of alkali-metal cations from theelectroactive cathode materials in the composite cathode to theelectrolyte and also retards the transport of anionic reduction productsfrom the composite cathode to the electrolyte or other layers or partsof the cell.

Yet another embodiment of the present invention incorporates a cathodecomprising a coating of the electroactive sulfur-containing cathodematerial, binders, electrolytes, conductive additives on a currentcollector. This resulting cathode is encapsulated, or otherwiseeffectively separated from the electrolyte layer, by a coherent filmcoating or impregnation comprising one or more electroactive transitionmetal chalcogenides. Such a cathode is illustrated in FIG. 3. Here, theprismatic sulfur-containing cathode structure 8 in contact with thecurrent collector 2 is effectively encapsulated with a layer of theelectroactive transition metal chalcogenide composition 9. Either orboth of the electroactive sulfur-containing cathode material and theelectroactive transition metal chalcogenide material may optionallycontain binders, electrolytes, and conductive fillers. Of course, ifsuch a composite cathode is to be used in combination with a solidelectrolyte, one need only employ an effective layer of the transitionmetal chalcogenide between the solid electrolyte and the cathodestructure rather than coating the entire cathode structure.

Still another embodiment of the present invention is shown in FIG. 4,which illustrates a prismatic composite cathode structure 1 in contactwith a current collector 2 and comprising a highly porous, fibrous, andultrafine sponge-like structure or network of an aerogel or xerogel ofan electroactive transition metal chalcogenide composition 10 into whichthe electroactive sulfur-containing cathode materials 11 are embedded orencapsulated. The fibrous nature of such aerogel and xerogel materialsis described, for example, by Chaput et al., J. Non-Cryst. Solids 1995,118, 11-18, and references therein. Again, the electroactive transitionmetal chalcogenide matrix optionally contains a binder, an electrolyte,and/or a conductive additive.

For the composite cathode structures which employ a composite cathodebound to a current collector, such as those illustrated FIGS. 1, 2, and4, preferred electroactive transition metal chalcogenides are thosewhich yield composite cathodes having good adhesion to the metal currentcollector. The use of such materials can greatly facilitate thecollection of current from the composite cathode and improve theintegrity of the cathode structure.

In one embodiment of the present invention, the composite cathode is aparticulate, porous electroactive transition metal chalcogenidecomposition, optionally containing non-electroactive metal oxides, suchas silica, alumina, and silicates, that is further impregnated with asoluble electroactive sulfur-containing cathode material. This isespecially beneficial in increasing the energy density and capacityabove that achieved with the electroactive sulfur-containing cathodematerial (e.g., electroactive organo-sulfur and carbon-sulfur cathodematerials) only.

The relative amounts of electroactive transition metal chalcogenide andelectroactive sulfur-containing cathode material in the compositecathode can vary widely so long as sufficient electroactive transitionmetal chalcogenide is present to effectively retard anionic reductionproducts from out-diffusing into the surrounding medium or layer whileeffectively maintaining or improving the capacity and cell efficiencies.Typically, the amount of electroactive transition metal chalcogenideused in the complete composite cathode will vary from 2 wt % to about 70wt %. When used in a separate layer of the composite cathode, such as inFIG. 3, the amount of electroactive transition metal chalcogenide in theseparate layer only will vary from about 5 wt % to 100 wt %. Preferredcomposite cathodes are those that contain between about 5 wt % and 50 wt% electroactive transition metal chalcogenide compounds, and mostpreferred composite cathodes contain between about 5 wt % and 40 wt %electroactive transition metal chalcogenide compounds.

The composite cathodes of the present invention may further comprise anon-electroactive metal oxide to further improve the fabrication as wellas the electrical and electrochemical properties of the resultingcathode. Examples of such non-electroactive metal oxides are silica,alumina, and silicates. Preferably, such metal oxides are porous innature, and have a high surface area of greater than 20 m²/g. Typically,the non-electroactive metal oxide material is incorporated or mixed withthe transition metal chalcogenide during fabrication of the compositecathode.

The composite cathodes of the present invention may further comprise oneor more materials selected from the group of binders, electrolytes, andconductive additives, usually to improve or simplify their fabricationas well as improve their electrical and electrochemical characteristics.Similarly, such materials may be used as a matrix for the electroactivesulfur-containing cathode material, the electroactive transition metalchalcogenide, or both.

The choice of binder material may vary widely so long as it is inertwith respect to the composite cathode materials. Useful binders arethose materials, usually polymeric, that allow for ease of processing ofbattery electrode composites and are generally known to those skilled inthe art of electrode fabrication. Examples of useful binders are organicpolymers such as polytetrafluoroethylene (s®), polyvinylidine fluorides(PVF₂ or PVDF), ethylene-propylene-diene (EPDM) rubbers, polyethyleneoxides (PEO), UV curable acrylates, UV curable methacrylates, and UVcurable divinylethers, and the like.

Useful conductive additives are those known to one skilled in the art ofelectrode fabrication and are such that they provide electricalconnectivity to the majority of the electroactive materials in thecomposite cathode. Examples of useful conductive fillers includeconductive carbons (e.g., carbon black), graphites, metal flakes, metalpowders, electrically conductive polymers, and the like.

Examples of useful electrolytes include any liquid, solid, or solid-likematerials capable of storing and transporting ions, so long as theelectrolyte material is chemically inert with respect to the compositecathode material and the electrolyte material facilitates thetransportation of ions.

In those cases where binder and conductive filler are desired, theamounts of binder and conductive filler can vary widely and the amountspresent will depend on the desired performance. Typically, when bindersand conductive fillers are used, the amount of binder will vary greatly,but will generally be less than about 15 wt % of the composite cathode.Preferred amounts are less than 10 wt %. The amount of conductive fillerused will also vary greatly and will typically be less than 15 wt % ofthe composite cathode. Preferred amounts of conductive additives aregenerally less than 12 wt %.

Particularly preferred composite cathodes are those comprising anelectroactive sulfur-containing material (e.g., a carbon-sulfur polymeror elemental sulfur); V₂O₅; conductive carbon; and a PEO binder.

Methods of Making Composite Cathodes

One aspect of the present invention pertains to methods for fabricatingcomposite cathodes.

One method relates to the fabrication of composite cathodes by thephysical mixture of the electroactive sulfur-containing cathodematerial, the electroactive transition metal chalcogenide, andoptionally binders, electrolytes, and conductive fillers either as drysolids, or as a slurry in a solvent or mixtures of solvents. Theresulting mixture is then fabricated into a cathode structure of desireddimensions, for example, by casting, coating, dip-coating, extrusion,calendering, and other means known in the art.

Thus, in one embodiment, the present invention pertains to methods forpreparing the composite cathodes of the present invention, said methodscomprising the steps of:

(a) dissolving or dispersing an electroactive transition metalchalcogenide in a liquid medium;

(b) adding to the composition resulting from step (a) an electroactivesulfur-containing cathode material;

(c) mixing the composition resulting from step (b) to dissolve ordisperse said electroactive sulfur-containing cathode material, therebyforming a composition having a desired consistency and particle sizedistribution;

(d) casting the composition resulting from step (c) onto a suitablesubstrate or placing the composition resulting from step (c) into amold;

(e) removing some or all of the liquid from the composition resultingfrom step (d) to provide a solid or gel-like composite cathode structurein the shape or form desired; and

(f) optionally heating the composite cathode structure of step (e) to atemperature of 100° C. or greater.

Examples of liquid media suitable for use in the methods of the presentinvention include aqueous liquid, non-aqueous liquids, and mixturesthereof. Especially preferred liquids are non-aqueous liquids such asmethanol, ethanol, isopropanol, propanol, butanol, tetrahydrofuran,dimethoxyethane, acetone, toluene, xylene, acetonitrile, andcyclohexane. Most preferred liquids are those selected from the groupconsisting of acetone, acetonitrile, and dimethoxyethane.

Another method relates to the fabrication of a composite cathode by asol-gel method wherein the electroactive sulfur-containing cathodematerial, and optionally binders and conductive fillers, are suspendedor dispersed in a medium containing a sol (solution) of the desiredelectroactive transition metal chalcogenide composition; the resultingcomposition is first converted into a sol-gel (e.g., a gel-like materialhaving a sol-gel structure or a continuous network-like structure) bythe addition of a gelling agent, and the resulting sol-gel furtherfabricated into a composite cathode.

The electroactive transition metal chalcogenide sols are dispersions ofcolloidal particles in the liquid. Dispersions of colloidal particles ofthe electroactive transition metal chalcogenides can be prepared by avariety of methods known in the art, including, for example, the methodsdescribed in U.S. Pat. No. 4,203,769. From the sol, a sol-gel orgel-like material is formed which has an interconnected, rigid network,typically having submicron-sized pores. This network (e.g., oxidenetwork) is the result of an inorganic polymerization reaction.Typically the precursor for forming the sol-gel is a molecularderivative, such as an transition metal alkoxide or a transition metalacetylacetonate.

Thus, in one embodiment, the present invention pertains to methods forpreparing the composite cathodes of the present invention, said methodscomprising the steps of:

(a) dissolving or dispersing an electroactive transition metalchalcogenide in a liquid medium;

(b) adding to the composition resulting from step (a) an electroactivesulfur-containing cathode material;

(c) mixing the composition resulting from step (b) to dissolve ordisperse said electroactive sulfur-containing cathode material, therebyforming a composition having a desired consistency and particle sizedistribution;

(d) contacting the composition resulting from step (c) with a gellingagent, thereby forming a sol-gel having a desired viscosity;

(e) casting the composition resulting from step (d) onto a suitablesubstrate or placing the composition resulting from step (d) into amold;

(f) removing some or all of the liquid from the composition resultingfrom step (e) to provide a solid or gel-like composite cathode structurein the shape or form desired; and

(g) optionally heating the composite cathode structure of step (f) to atemperature of 100° C. or greater.

In another embodiment, the present invention pertains to methods forpreparing the composite cathodes of the present invention, said methodscomprising the steps of:

(a) dissolving an electroactive transition metal chalcogenide (e.g.,electroactive transition metal alkoxide or electroactive transitionmetal chalcogenide precursor) in a liquid medium;

(b) contacting the composition resulting from step (a) with a gellingagent, thereby forming a sol-gel having a desired viscosity;

(c) adding to the composition resulting from step (b) an electroactivesulfur-containing cathode material;

(d) mixing the composition resulting from step (c) to dissolve ordisperse said electroactive sulfur-containing cathode material, therebyforming a composition having a desired consistency and particle sizedistribution;

(e) casting the composition resulting from step (d) onto a suitablesubstrate or placing the composition resulting from step (d) into amold;

(f) removing some or all of the liquid from the composition resultingfrom step (e) to provide a solid or gel-like composite cathode structurein the shape or form desired; and

(g) optionally heating the composite cathode structure of step (f) to atemperature of 100° C. or greater.

Gelling agents that can effectively cause the electroactive transitionmetal chalcogenide to form a sol-gel (e.g., a gel-like or networkstructure) include both chemical and physical agents. Useful chemicalgelling agents are those that convert the electroactive transition metalchalcogenide to a form with lower solubility in the liquid medium used.Typical effective chemical agents are water, and lower alcohols such asmethanol, ethanol, ispropanol, ethylene glycol, and the like. Otheruseful chemical gelling agents are non-solvents for the electroactivetransition metal chalcogenide, acids, and polymeric binders. With theaddition of small amounts of non-solvent, the electroactive transitionmetal chalcogenide will gradually precipitate giving rise to powders orgel-like structures. Useful physical gelling agents are heating,cooling, light, x-rays, and electron beams. Thus, the application ofheat may cause decomposition of alkoxy groups or other functional groupsin a electroactive transition metal compound leading to a newcomposition with a networked structure giving rise to a gel. Likewise,the application of light, x-rays, or electron beams may causedecomposition or crosslinking of the alkyl groups or other functionalgroups, giving rise to a gel or precipitated slurry of the compositecathode.

This sol-gel method can be used to provide composite cathodes in atleast two different configurations. One relates to a configuration inwhich particulate electroactive sulfur-containing cathode material isencapsulated with a layer of the electroactive transition metalchalcogenide composition. The other relates to a configuration in whichthe electroactive sulfur-containing cathode material is embedded in acontinuous network or continuous phase of the electroactive transitionmetal chalcogenide composition. The transition metal chalcogenide phasecan be viewed as an interfacial boundary layer around the particulateelectroactive sulfur-containing cathode material. This boundary layerhas a high concentration of interconnecting nanoscale porosity.

In another embodiment, the present invention pertains to methods forpreparing the composite cathodes of the present invention, said methodscomprising the steps of:

(a) coating a current collector substrate with a composition comprisingan electroactive sulfur-containing cathode material and drying or curingsaid composition to form a solid or gel-type electroactive cathode layeron said current collector substrate;

(b) dissolving or dispersing an electroactive transition metalchalcogenide in a liquid medium;

(c) coating said electroactive cathode layer with the compositionresulting from step (b) and drying or curing said composition to form asolid layer of said electroactive transition metal chalcogenidecomposition which covers the outer surface of said electroactive cathodelayer.

In another embodiment, the present invention pertains to methods forpreparing the composite cathodes of the present invention, said methodscomprising the steps of:

(a) coating a current collector substrate with a composition comprisingan electroactive sulfur-containing cathode material and drying or curingsaid composition to form a solid or gel-type electroactive cathode layeron said current collector substrate;

(b) dissolving or dispersing an electroactive transition metalchalcogenide in a liquid medium;

(c) contacting the composition resulting from step (b) with a gellingagent, thereby forming a sol-gel having a desired viscosity;

(d) coating said electroactive cathode layer with the compositionresulting from step (c) and drying or curing said composition to form asolid layer of said electroactive transition metal chalcogenidecomposition which covers the outer surface of said electroactive cathodelayer.

Examples of electroactive transition metal chalcogenides andelectroactive sulfur-containing cathode materials for use in the abovemethods are described in detail above.

The temperature at which various components in the above processes aredissolved or dispersed is not critical and any temperature can be usedso long as the desired solution or dispersion of the components in theliquid medium is obtained. For the fabrication of some compositecathodes it may be desirable to use higher temperatures so as to effectdissolution of one or more components during the process. A lowertemperature may then be desired so as to effectively cause one or morecomponents to separate out in a gel or precipitate form. Usefultemperatures can be routinely determined experimentally by one skilledin the art. Preferred temperatures are those at which the transitionmetal chalcogenide initially dissolves or forms a colloidal solution inthe liquid medium. Especially preferred temperatures are those whichfurther provide for an economical process. Most preferred temperaturesare those which further are close to room temperature or slightly above.

Optionally, binders, electrolytes, and conductive fillers may be addedto the compositions at one or more of the various steps in the methodsdescribed above, usually at steps which involve dissolving, dispersing,or mixing. Such additives often facilitate or improve adhesion,cohesion, current collection, and ion transport.

Mixing of the various compositions in the methods described above can beaccomplished by a variety of methods so long as the desired dispersionof the materials is obtained. Suitable methods of mixing includemechanical agitation, grinding, ultrasonication, ball-milling, sandmilling, impingement milling, and the like.

Removal of some or all of the liquid from the various compositions inthe methods described above can be accomplished by a variety ofconventional means, so long as the resulting product has a desiredporosity and/or pore size distribution, surface area, shape, chemicalcomposition, adhesion to the current collector or other substrate, andthe like. Useful methods for removal of liquid employ forced hot airconvection, heat, infrared radiation, flowing gases, vacuum, reducedpressure, extraction, and the like. Preferred methods for removal ofliquid include forced hot air convection, vacuum evaporation, reducedpressure, infrared heating, and flowing gas. Most preferred methodsinvolve a combination of these preferred techniques.

It is well known in the art of battery electrode fabrication that, bycasting a slurry of electrode components and removing the solvent, thinfilms and coatings with the desired thickness can be made. One of skillin the art will appreciate that, by flash evaporation of the solventfrom a slurry of the electroactive transition metal chalcogenide and theelectroactive sulfur-containing cathode material, one can produce finelydivided powders with varying particle sizes. Powdered composite cathodematerials prepared by the processes of the present invention can be hotor cold pressed, slurry coated or extruded onto current collectingmaterials by techniques known to those skilled in the art of batteryelectrode fabrication.

Examples of preferred composite cathodes prepared using the processes ofthe present invention include thin film structures up to about 25 μm inthickness, coatings on current collectors up to about 100 μm inthickness, and powdered composite structures.

Composite cathodes with the configuration shown in FIG. 3 can also befabricated by vacuum evaporation of the electroactive transition metalchalcogenide composition on top of the electroactive sulfur-containingcathode material. Films and membranes of transition metal chalcogenidecompounds such as V₂O₅ and MnO₂ can be deposited in vacuum using severaltechniques, including sputtering and electron-beam evaporation (e-beam)using target materials of the same. Both sputtering and e-beam may bedone as reactive evaporation with a partial oxygen pressure in order toachieve the proper stoichiometry. Plasma spraying may also beapplicable. Vacuum evaporation fabrication of composite cathodes of thepresent invention is preferred when said composite cathode material isused in an all solid-state cell fabricated using vacuum web coatingtechnologies for most or all of the layers in the cell.

Rechargeable Battery Cells and Methods of Making Same

One aspect of the present invention pertains to a rechargeable, electriccurrent producing cell which comprises:

(a) an anode,

(b) a composite cathode of the present invention, and

(c) an electrolyte that is stable in the presence of the anode andcathode.

Another aspect of the present invention pertains to methods of forming arechargeable, electric current producing cell, said method comprisingthe steps of:

(a) providing an anode;

(b) providing a composite cathode of the present invention; and,

(c) enclosing an electrolyte between said anode and said compositecathode.

The anode material may be comprised of one or more metals or metalalloys or a mixture of one or more metals and one or more alloys,wherein said metals are selected from the Group IA and IIA metals in thePeriodic Table. Anodes comprising lithium and sodium are useful for theanode of the battery of the invention. The anode may also bealkali-metal intercalated carbon, such as LiC_(x) where x is equal to orgreater than 2. Also useful as anode materials of the present inventionare alkali-metal intercalated conductive polymers, such as lithium,sodium or potassium doped polyacetylenes, polyphenylenes,polyquinolines, and the like. Examples of suitable anodes includelithium metal, lithium-aluminum alloys, lithium-tin alloys,lithium-carbon, lithium-graphite, calcium metal, aluminum, sodium,sodium alloys, and the like. Preferred anodes are those selected fromthe group of lithium metal and lithium-aluminum and lithium-tin alloys.

The electrolytes used in battery cells function as a medium for storageand transport of ions, and in the special case of solid electrolytesthese materials additionally function as separator materials between theanodes and cathodes. Any liquid, solid, or solid-like material capableof storing and transporting ions may be used, so long as the material ischemically inert with respect to the anode and the cathode and thematerial facilitates the transportation of ions between the anode andthe cathode.

Examples of useful electrolytes are solid electrolyte separatorscomprised of polyethers, PEO, polyimides, polyphosphazenes,polyacrylonitriles (PAN), polysiloxanes, polyether graftedpolysiloxanes, derivatives of the foregoing, copolymers of theforegoing, crosslinked and network structures of the foregoing, blendsof the foregoing, and the like to which is added an appropriateelectrolyte salt.

Examples of useful gel-polymer electrolytes are those prepared frompolymer matrices derived from polyethylene oxides, polypropylene oxides,polyacrylonitriles, polysiloxanes, polyimides, polyethers, sulfonatedpolyimides, perfluorinated membranes (Nafion™ resins), divinylpolyethylene glycols, polyethylene glycol-bis-(methyl acrylates),polyethylene glycol-bis(methyl methacrylates), derivatives of theforegoing, copolymers of the foregoing, crosslinked and networkstructures of the foregoing, blends of the foregoing, and the like.

Examples of useful solvents or plasticizing agents as gel forming agentsfor electrolytes include ethylene carbonate (EC), propylene carbonate(PC), N-methyl acetamide, acetonitrile, sulfolane, tetraethyleneglycoldimethyl ether (TEGDME), 1,2-dimethoxyethane, polyethylene glycols,1,3-dioxolanes, glymes, siloxanes, and ethylene oxide grafted siloxanes,and blends thereof. Particularly preferred solvents and plasticizingagents are those derived from graft copolymers of ethylene oxide andoligomers of poly(dimethyl siloxane) of general formula X, as describedin U.S. Pat. No. 5,362,493,

wherein o is an integer equal to or greater than 1; p is an integerequal to or greater than 0 and less than about 30; and, the ratio t/s isequal to or greater than 0. Values for o, p, s, and t can vary widelyand depend on the desired properties for said liquid or plasticizingagent. Preferred agents of this type are those wherein o ranges fromabout 1 to 5, p ranges from about 1 to 20, and the ratio t/s is equal toor greater than 0.5. An especially preferred composition of formula X isthat in which o is equal to 3, p is equal to 7, and the ratio of t to sis 1.

These liquid or plasticizing agents themselves, and blends thereof, areuseful solvents to form liquid electrolytes which provide othereffective electrolyte systems for the cells of the present invention.For example, glymes or sulfolane with lithium salts, such as LiAsF₆, areuseful liquid electrolytes. 1,3-Dioxolane and TEGDME are especiallyuseful as a blend of solvents for liquid electrolytes. Likewise,compositions of TEGDME or of formula X together with LiSO₃CF₃ areespecially useful as liquid electrolytes.

Examples of ionic electrolyte salts for electrolytes include MClO4,MAsF6, MSO₃CF₃, MSO₃CH₃, MBF₄, MB(Ph)₄, MPF₆, MC(SO₂CF₃)₃, MN(SO₂CF₃)₃,MN(SO₂CF₃)₂,

and the like, where M is Li or Na. Other electrolytes useful in thepractice of this invention are disclosed in U.S. Pat. No. 5,538,812.

EXAMPLES

Several embodiments of the present invention are described in thefollowing examples, which are offered by way of illustration and not byway of limitation.

Example 1

This example describes the fabrication of a composite cathode of thepresent invention. Vanadium oxide isopropoxide (25 mL, Alpha AESAR Co.)was placed in a dry flask and 500 mL of acetone (having 0.5% water) wasadded drop wise to the alkoxide liquid with constant stirring. Theamount of acetone added was based on getting a final concentration ofvanadium pentoxide (V₂O₅) in the sol (solution) of 4 g/100 mL. Aftermixing the vanadium oxide isopropoxide with acetone, a mixture ofwater-acetone (1 to 10 by volume) was added drop wise; the total molarratio of water to vanadium alkoxide was 0.5, including the water presentin the acetone. The color of the sol was yellow to orange. The molarratio of water to alkoxide can be varied in the range 0.5 to 3.0,depending on the subsequent slurry and coating procedure desired.

A slurry of a electroactive sulfur-containing cathode material was madewith the sol prepared above. A requisite amount of sulfur was taken in amortar and a proportionate amount of sol was added to the agate mortar.The mixture was gently ground for 15 minutes. Dry carbon powder(Shawinigan 50AB black, hereafter designated as SAB) was then added andthe mixture was ground again for 15 minutes with an additional amount ofacetone being added. The composition of the slurry as expressed in termsof sulfur, vanadium pentoxide and carbon black was as follows: sulfur 80wt %, V2O5 15 wt % and carbon 5 wt %. This slurry was deposited onnickel foil using a doctor blade in a hood under ambient atmosphere. Thecoating was dried under an IR lamp overnight in ambient atmosphere. Thecoating after IR drying was further dried in a vacuum oven at 50° C. forone hour yielding the composite cathode on the current collector.

Example 2

In this example, a sulfur-containing composite cathode of the presentinvention with the configuration shown in FIG. 3 was fabricated on anickel foil current collector substrate. The composition of theelectroactive sulfur-containing cathode layer was as follows: 44 wt %sulfur, 26 wt % carbon (SAB), and 30 wt % of a UV curable bindercomprising 25 wt % polyethyleneglycol dimethacrylate, 25 wt %polyethyleneglycol divinylether, and 50 wt % polyethyleneglycoldimethylether. After UV curing of the cathode layer, thesulfur-containing cathode layer was coated with the V₂O₅ sol prepared inExample 1 using a dipping technique. Two dippings were made.Subsequently, the coated composite cathode was dried in a vacuum oven at60° C. for an hour.

It was noted that the sulfur-containing cathode layer obtained bycasting of the slurry was porous. It was found that the sol miximpregnated through the pores in the sulfur-containing cathode layer andformed a thin V₂O₅ gel layer at the pore boundaries as well as over theentire structure. It is anticipated that because of the low viscosity ofthe V₂O₅ sol, impregnation into the finer pores is also likely.

Example 3

Vanadium oxide isopropoxide (12.53 mL, Alpha AESAR Chemical Co.) wasdissolved in anhydrous ethylene glycol dimethyl ether (DME) resulting ina slightly yellow solution. Subsequently 4.0 mL of a solution of 0.4644g of water in 5 mL DME was added dropwise over 30 minutes at 20° C. withstirring under dry argon. The resulting yellow-brown, slightlytranslucent sol was stirred for 2.5 hour and stored under positive argonpressure. The concentration of vanadium oxide in the as synthesized solwas 4.4 g/100 mL. To this sol was added powdered sulfur and conductivecarbon with mixing to make a slurry. Prior to use, the sulfur and carbonwere dried in an oven at 60° C. and 180° C., respectively andsubsequently stored in a dry room.

The slurry was processed using a ball milling technique. The jars andbeakers used for the slurry making were dried in an oven at 110° C. forseveral hours and were stored in a dry room. The powdered sulfur wasfirst mixed with the vanadium sol in a ball mill for 1 hour. Then, thecarbon black (SAB) was added and the milling process continued. After 1hour an additional amount of DME solvent was added to reduce the solidcontent to about 12 g/100 mL and the milling resumed for another 3hours. This slurry was then cast onto a nickel foil by the doctor bladetechnique in a hood under ambient conditions. The wet coating was leftovernight in a hood to air dry. The coating was then heat treated in anoven at 110° C. for 1 hour and then subsequently in a vacuum oven at 60°C. for 1 hour. The composition of the dry composite cathode was 75 wt %sulfur, 15 wt % V₂O₅ and 10 wt % C.

Example 4

A slurry similar to that described in Example 3 was made using avanadium sol with acetone as solvent instead of DME. The molar ratio ofwater to alkoxide was 0.5. The procedure used to make the slurry wassimilar to that described in Example 3 with acetone as the solvent and amilling time of 15 hours. The conditions of deposition of the coating,drying and heat treatment were the same as that described in Example 3.The composition of the dried composite cathode was 80 wt % sulfur, 15 wt% V₂O₅, and 5 wt % conductive carbon. The cast composite cathode layerwas 25 μm thick after drying.

Example 5

This example describes the fabrication and performance of floodedbattery cells comprising the composite cathodes of the presentinvention. A working electrode with a composite cathode made by theprocedure described in Example 1, prepared by dipping a Pt disk (0.015cm²) into the slurry of the carbon, sulfur, and vanadium pentoxidecomposite followed by drying under an IR-lamp, was immersed into anundivided electrochemical cell with lithium wire and lithium foil asreference and counter electrodes, respectively. The cell was filled witha 1 M solution of lithium triflate in electrolyte grade TEGDME.

Cyclic voltammograms of the electrode recorded at a scan rate of 1 mV/sat 25° C. are shown in FIG. 5. Three quasi-reversiblereduction-oxidation peaks corresponding to formation of δ-V₂O₅ and twosteps of sulfur reduction confirm the composite nature of the material.Continuous cycling between 1.5 and 4.4 V results in decrease of bothsulfur-related peaks. However, the electrode retains its integrity,indicating improved adhesion to the Pt surface. Parallel increase of thevanadium oxide peaks allows one to assume that some interconversion ofmaterial takes place, probably with formation of the ω-phase of vanadiumpentoxide or a mixed vanadium oxo-sulfide. Such interconversionresulting in the increase of the apparent cathode potential should besuitable for improved battery performance.

Example 6

A working electrode, prepared by dipping a large area Pt currentcollector (2 cm²) into the final slurry before coating of thecarbon-sulfur-vanadium pentoxide composite of Example 3, followed bydrying under an IR-lamp, was immersed into a 3-compartmentelectrochemical cell separated by glass filter membranes. The cell wasfilled with a 1 M solution of lithium triflate in electrolyte gradeTEGDME. Lithium wire and lithium foil were used as reference and counterelectrodes, respectively.

The working electrode was galvanostatically charged/discharged at acurrent density of 0.1 mA/cm². Discharge curves at 25° C. are shown inFIG. 6. A significant increase in the electrode mid-potential can beseen at the second discharge compared to the first one. Additionalcharge/discharge curves are shown in FIG. 7 which indicate theappearance of increased capacity with cycle number.

After 5 complete charge/discharge cycles, a small amount of theelectrolyte solution from the working electrode compartment was removedfor analysis. The UV-visible absorption spectrum of the solution isshown in FIG. 8( b). No significant absorption peaks in the 320-380 nmregion were observed, indicating the absence of sulfide and polysulfidespecies in the electrolyte. For comparison, a control sulfur-containingelectrode was prepared to compare the out-diffusion behavior of thiscathode without the transition metal chalcogenide layer. The controlcathode was made by dipping a Pt current collector (2 cm²) into a slurrycontaining 50% of elemental sulfur, 30% of carbon black (SAB), and 20%of UV-curable binder. A electrochemical cell with the UV-cured electrodewas assembled and tested as described above. A UV absorption spectrum ofthe electrolyte solution, taken after the first discharge, is shown inFIG. 8( a). A very strong absorption peak at about 350 nm owing todissolved sulfides and polysulfides is easily observed. FIG. 8( c) showsthe absorption spectrum of the electrolyte solution of both the controland the vanadium pentoxide electrodes of the example before the firstdischarge cycle, showing the absence of any appreciable amounts ofsulfides and polysulfides.

Example 7

This example describes the construction and performance of a button cellconstructed from the composite cathode made in Example 1. The buttoncell was fabricated by the conventional method. The electroactivematerial (sulfur) in the composite cathode layer was 1.36 mg/cm². TEGDMEelectrolyte with lithium triflate salt was used as a liquid electrolyte.The separator used was CELGARD™ 2500 (Hoechst Celanese Corporation), andthe anode was lithium metal. The cell was tested under the followingconditions: current density 0.1 mA/cm², cycling voltage 2.75 V to 1.85V. The cell capacity was initially around 504 mAh/g, but subsequentlyincreased to 956 mAh/g and remained stable without fade after 30 cycles.

Example 8

A button cell similar to that described in Example 7 was constructedusing the composite cathode fabricated in Example 2. The cell testingconditions were as follows: current density 0.1 mA/cm², cycling voltage2.75 V to 1.85, 10 hours time limited. The initial cell capacity wasaround 1382 mAh/g. After 81 cycles the capacity was 738 mAh/g.

Example 9

A button cell was fabricated using the composite cathode of Example 3using the conventional button cell configuration. A liquid electrolytehaving TEGDME with lithium triflate salt was used as electrolyte.Celgard™ 2500 was used as a separator. The composite cathode providedthe cell performance shown in Table 1.

TABLE 1 Thickness Capacity (mAh/g) Capacity (mAh/g) Capacity (mAh/g)(μm) Coating at 0.1 mA/cm² at 0.2 mA/cm² at 0.3 mA/cm² weight (g) (atcycle no.) (at cycle no.) (at cycle no.) 45 μm  900 mAh/g 450 to 380mAh/g 520 mAh/g   2 mg/cm² (4) (76) (46) 50 μm 1270 mAh/g 600 mAh/g Nodata. 1.2 mg/cm² (1) (5) 25 μm  880 mAh/g 700 mAh/g No data   2 mg/cm²(2) (8)

Example 10

Button cells similar to those fabricated in Example 9 were fabricatedusing the composite cathode of Example 4. The thickness of the cathodelayer was 25 μm and the amount of sulfur as electroactive material was1.0 mg/cm². Evaluation of the cell performance gave the results shown inFIG. 9. The initial capacity at 0.1 mA/cm² was 1172 mAh/g, and thecapacity after 20 cycles was 1103 mAh/g.

Example 11

This example describes the fabrication of a composite cathode containingconductive carbon and a polymeric binder. Elemental sulfur was ground inan IKA grinder for 5 seconds. Into a dry ceramic ball mill jarcontaining 35 pieces of ceramic cylinders was added 8.7 g of the groundsulfur, 1.5 g of dry V₂O₅ aerogel powder prepared by supercriticalextraction of the solvent from a vanadium acetylacetonate sol, 3.0 g ofdry conductive carbon (SAB), and 72 g of a 2.5 wt % solution ofpolyethylene oxide binder in acetonitrile. The jar was sealed and putonto the ball mill at a high speed of revolution for 22 hours. Themilling was stopped and a sample of the slurry was withdrawn foranalysis. The mean particle size was 6.4 μm, and the slurry exhibited aviscosity of 1142 cp 10 s⁻¹ and 58 cp at 740 s⁻¹ as determined by aRheometrics model DSR200. This slurry was then used to cast hand drawncoatings onto both sides of a 17.5 μm thick nickel foil substrate with awet thickness of 325 μm on each side. The coatings were dried underambient conditions overnight, then further dried under vacuum at 60° C.for one hour. The resulting dry coating thickness was 75 μm on eachside, and the weight of the electroactive cathode material was 1.09mg/cm². The apparent density of the composite cathode was 0.496 g/cm³.

Example 12

This example describes the fabrication and performance of AA sized cellsconstructed using the composite cathode made in Example 11. On top ofone side of the composite cathode structure fabricated in Example 11 wasplaced a piece of Celgard 2500 separator and on top of this was placed apiece of lithium foil (Cyprus, 50 μm thick). This set of sandwichedbattery electrodes was then rolled up into a “jelly roll” configurationand placed into a AA battery sized metal container. The container wasfilled with the electrolyte comprising 1 M lithium triflate in TEGDME,and the lid was sealed onto the container after making the appropriateinternal connections. The battery cell was then discharged and chargedfor 400 cycles. The first discharge cycle exhibited a total capacity of726 mAH and a specific capacity for the electroactive cathode materialof 1232 mAh/g. By the third cycle, the total capacity of the cell wasfairly steady between 387-396 mAh, and the specific capacity was 650-670mAh/g.

Example 13

This example describes the fabrication of a composite cathode containinga carbon-sulfur polymer of general formula VI, where z was 4.8. Theprocedure of Examples 11 and 12 were followed except that acarbon-sulfur polymer of formula VI, where z was 4.8, was substituted inequal amounts for the ground sulfur. The resulting dry coating thicknesswas 44 μm on each side, and the weight of the electroactive cathodematerial was 0.77 mg/cm².

The first discharge cycle exhibited a total capacity of 495 mAh and aspecific capacity for the electroactive cathode material of 1269 mAh/g.By the fifth cycle, the total capacity of the cell was fairly steadybetween 165-218 mAh, and the specific capacity was 417-559 mAh/g.

Example 14

The following procedures was used to prepare transition metalchalcogenides impregnated with soluble electroactive sulfur-containingcathode species.

To 500 mL of toluene was added 72 g of sulfur and 48 g of vanadium oxideaerogel powder. The mixture was refluxed at 110° C. for 3 hours withconstant stirring. The product was filtered and washed with acetone anddried in vacuum at 90° C. for 4 hours. The sulfur content of theimpregnated product was 57.3 wt %.

By varying the relative amount of sulfur compared to the aerogel, thesulfur content of impregnated aerogel could be varied from 50 wt % to 82wt %. Elemental analysis has shown the final impregnated productcontains small amounts of carbon. An elemental analysis ofsulfur-impregnated vanadia aerogel with 76.81 wt % sulfur content showed18.49 wt % vanadium, 0.54 wt % carbon, and 4.16 wt % oxygen (calculatedby difference).

Example 15

This example describes the fabrication of composite cathodes containingsulfur impregnated aerogel powder prepared as described in Example 14with an overall content of electroactive material of 55 wt % sulfur and45 wt % vanadium oxide. The sulfur-impregnated aerogel was ground in anagate mortar to break agglomerates and produce a fine powder. To a ballmill jar containing ceramic cylinders was added 45 g of elementalsulfur, 22.5 g of the sulfur-impregnated (55 wt % sulfur) vanadiaaerogel, 13.5 g of carbon (SAB) and 90 g of a 1 wt % solution ofpolyethylene oxide dissolved in a mixed solvent of methyl acetate andn-propanol (90:10 wt ratio). The solid content of the slurry was 11 wt%. The mixture was ball milled for 22 hours. The slurry was cast handdrawn onto both sides of a 18 μm thick conductive carbon coated aluminumfoil (Rexam Graphics, South Hadley, Mass.) as a current collector. Thecoatings were dried under ambient conditions overnight, and then undervacuum at 60° C. for one hour. The resulting dry cathode coating had athickness in the range of 60 to 70 μm on each side of the currentcollector, with a density of electroactive cathode material in the rangeof 2.1 mg/cm² to 2.7 mg/cm². The volumetric density of the electroactivematerials was 293 to 389 mg/cm³.

Wound AA size cells were fabricated from these cathodes with a 4 mil(0.1 mm) lithium anode and a TONEN™ (Tonen Chemical Corporation)polyolefin separator. The cells were filled with a liquid electrolyte(50% 1,3-dioxolane, 20% diglyme, 10% sulfolane and 20% dimethoxyethane(DME) by volume). The cells were cycled at a rate of charge anddischarge of 0.32 mA/cm² and 0.5 mA/cm² respectively. Cell performancedata showed that these cathodes had good capacity and stability. Theyshowed a low rate of capacity loss with cycling with values ranging from0.003 to 1.7 mAh/cycle for the first 50 cycles. In some cells thecapacity actually increased up to the 25th cycle at rates ranging from0.32 to 1.32 mAh/cycle.

Example 16

This example describes the cathode design and process whereby a coatingof sulfur-containing electroactive cathode material is coated with alayer of electroactive transition metal chalcogenide. Cathodes preparedfrom a slurry coating on a conductive carbon coated aluminum foil (RexamGraphics, South Hadley, Mass.) as a current collector with a compositionof 53 wt % sulfur, 16 wt % carbon (SAB), 26 wt % V₂O₅ and 5 wt % PEO,were coated with a barrier layer of vanadia sol. The coating layer wasprepared by dissolving 2 wt % vanadium oxide tri-isopropoxide and 0.75wt % polyethylene oxide (molecular weight 5,000,000) in a 90:10methylacetate/n-propanol solvent blend and hand coating this solutionusing the doctor blade technique on top of the dried cathode. Thecoating layer thickness was approximately 10 μm and the amount ofvanadia xerogel in the layer was in the range of 0.25 to 0.4 mg/cm². Anidentical cathode without a barrier coating was used as a control. WoundAA cells were constructed from the above cathodes using a 3 mil (0.075mm) lithium anode and a TONEN™ separator. An liquid electrolyteconsisting of 50% 1,3-dioxolane, 20% diglyme, 10% sulfolane and 20%dimethoxyethane (DME) (by volume) was used. FIG. 10 shows data fortypical AA wound cells with the vanadia xerogel coated cathode (●) andan uncoated control cathode (▪) cycled at a charge and discharge rate of0.57 mA/cm². It is evident from this data that the vanadia xerogelcoating layer has a significant positive effect on the specific capacityof the cathode and on the reduction of capacity fading with cycling.

Example 17

In a second approach to that described in example 16, amorphoussubmicron vanadia aerogel powders were dispersed in a PEO polymer matrixin a 70:30 ratio by weight. A 4 wt % solids dispersion of this mixturein acetonitrile was applied to the surface of a control cathode sheetsimilar to that of Example 16 by either a dipping or doctor bladetechnique. The thickness of the coating layer was in the range of 5 to 7μm. Cycling data from these cells showed a similar increase in thespecific capacities and in the reduction of capacity fading withcycling, compared to the control with no vanadia aerogel overcoating, asshown in Example 16.

While the invention has been described in detail and with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made without departingfrom the spirit and scope thereof.

1. A method of preparing a cathode comprising elemental sulfur, themethod comprising the steps of: (a) grinding elemental sulfur; (b)preparing a slurry comprising the ground elemental sulfur of step (a)and a liquid medium, wherein the slurry further comprises a conductiveadditive; a binder; a non-electroactive metal oxide; an electrolyte; andan electroactive transition metal chalcogenide; (c) coating the slurryof step (b) onto a substrate to form a coating layer; and (d) removingsome or all of the liquid from the coating layer to form a cathode,wherein: the mean particle size of particles in the slurry is 6.4 μm andthe substrate is a current collector.
 2. The method of claim 1, whereinthe thickness of the cathode is about 25 μm or less.
 3. The method ofclaim 1, wherein the thickness of the cathode about 100 μm or less. 4.The method of claim 1, wherein the apparent density of the cathode is0.496 g/cm³.
 5. The method of claim 1, wherein the cathode is porous. 6.The method of claim 1, wherein the liquid medium is a solvent.
 7. Themethod of claim 1, wherein the conductive additive comprises one or moreof the group consisting of conductive carbons, graphites, metal flakes,metal powders, and conductive polymers.
 8. The method of claim 1,wherein the binder comprises one or more of the group consisting ofpolytetrafluoroethylene, polyvinylidene fluorides,ethylene-propylene-diene rubbers, polyethylene oxides, UV curableacrylates, UV curable methacrylates, and UV curable divinyl ethers. 9.The method of claim 1, wherein the non-electroactive metal oxidecomprises one or more of the group consisting of silicas, aluminas andsilicates.
 10. The method of claim 1, wherein the electrolyte comprisesone or more of the group consisting of liquid electrolytes, gelelectrolytes and solid electrolytes.
 11. A method of preparing a cathodecomprising a carbon-sulfur polymer, the method comprising the steps of:(a) preparing a slurry comprising the carbon-sulfur polymer and a liquidmedium, wherein the carbon-sulfur polymer comprises particles, eachparticle has a diameter less than 10 μm, and the slurry furthercomprises an electrolyte; (b) coating the slurry of step (a) onto asubstrate to form a coating layer; and (c) removing some or all of theliquid from the coating layer to form the cathode.
 12. The method ofclaim 11, wherein the thickness of the cathode is about 25 μm or less.13. The method of claim 11, wherein the thickness of the cathode isabout 100 μm or less.
 14. The method of claim 11, wherein the apparentdensity of the cathode is 0.496 g/cm³.
 15. The method of claim 11,wherein the mean particle size of particles in the slurry is 6.4 μm. 16.The method of claim 11, wherein the cathode is porous.
 17. The method ofclaim 11, wherein the liquid medium is a solvent.
 18. The method ofclaim 11, wherein the slurry further comprises a conductive additive.19. The method of claim 18, wherein the conductive additive comprisesone or more of the group consisting of conductive carbons, graphites,metal flakes, metal powders, and conductive polymers.
 20. The method ofclaim 11, wherein the slurry further comprises a binder.
 21. The methodof claim 20, wherein the binder comprises one or more of the groupconsisting of polytetrafluoroethylene, polyvinylidene fluorides,ethylene propylene diene rubbers, polyethylene oxides, UV curableacrylates, UV curable methacrylates, and UV curable divinyl ethers. 22.The method of claim 11, wherein the slurry further comprises anon-electroactive metal oxide.
 23. The method of claim 22, wherein thenon-electroactive metal oxide comprises one or more of the groupconsisting of silicas, aluminas and silicates.
 24. The method of claim11, wherein the slurry further comprises an electrolyte.
 25. The methodof claim 24, wherein the electrolyte comprises one or more of the groupconsisting of liquid electrolytes, gel electrolytes and solidelectrolytes.
 26. The method of claim 11, wherein the slurry furthercomprises an electroactive transition metal chalcogenide.
 27. The methodof claim 11, wherein the substrate is a current collector.
 28. A cathodefor an electrochemical cell comprising elemental sulfur, wherein theapparent density of the cathode is 0.496 g/cm².
 29. The cathode of claim28, wherein the elemental sulfur comprises particles, wherein eachparticle has a diameter of generally less than 10 μm.
 30. The cathode ofclaim 28, wherein the thickness of the cathode is about 25 μm or less.31. The cathode of claim 28, wherein the thickness of the cathode isabout 100 μm or less.
 32. The cathode of claim 28, wherein the cathodefurther comprises a conductive additive.
 33. The cathode of claim 32,wherein the conductive additive comprises one or more of the groupconsisting of conductive carbons, graphites, metal flakes, metalpowders, and conductive polymers.
 34. The cathode of claim 28, whereinthe cathode further comprises a binder.
 35. The cathode of claim 34,wherein the binder comprises one or more of the group consisting ofpolytetrafluoroethylene, polyvinylidene fluorides,ethylene-propylene-diene rubbers, polyethylene oxides, UV curableacrylates, UV curable methacrylates, and UV curable divinyl ethers. 36.The cathode of claim 28, wherein the cathode further comprises anelectrolyte.
 37. The cathode of claim 36, wherein the electrolytecomprises one or more of the group consisting of liquid electrolytes,gel electrolytes and solid electrolytes.
 38. The cathode of claim 28,wherein the cathode further comprises a non-electroactive metal oxide.39. The cathode of claim 38, wherein the non-electroactive metal oxidecomprises one or more of the group consisting of silicas, aluminas andsilicates.
 40. The cathode of claim 28, wherein the slurry furthercomprises an electroactive transition metal chalcogenide.
 41. Anelectrochemical cell comprising: (a) an anode comprising lithium; (b) acathode comprising elemental sulfur or a carbon-sulfur polymer; and (c)an electrolyte; wherein the elemental sulfur or carbon-sulfur polymercomprises particles, wherein each particle has a diameter of less than10 μm.
 42. The cell of claim 41, wherein the apparent density of thecathode is 0.496 g/cm³.
 43. The cell of claim 41, wherein the thicknessof the cathode is about 25 μm or less.
 44. The cell of claim 41, whereinthe thickness of the cathode is about 100 μm or less.
 45. The cell ofclaim 41, wherein the cathode further comprises a conductive additive.46. The cell of claim 45, wherein the conductive additive comprises oneor more of the group consisting of conductive carbons, graphites, metalflakes, metal powders, and conductive polymers.
 47. The cell of claim41, wherein the cathode further comprises a binder.
 48. The cell ofclaim 47, wherein the binder comprises one or more of the groupconsisting of polytetrafluoroethylene, polyvinylidene fluorides,ethylene-propylene-diene rubbers, polyethylene oxides, UV curableacrylates, UV curable methacrylates, and UV curable divinyl ethers. 49.The cell of claim 41, wherein the cathode further comprises anelectrolyte.
 50. The cell of claim 49, wherein the electrolyte comprisesone or more of the group consisting of liquid electrolytes, gelelectrolytes and solid electrolytes.
 51. The cell of claim 41, whereinthe cathode further comprises a non-electroactive metal oxide.
 52. Thecell of claim 51, wherein the non-electroactive metal oxide comprisesone or more of the group consisting of silicas, aluminas and silicates.53. The cell of claim 41, wherein the slurry further comprises anelectroactive transition metal chalcogenide.
 54. The cell of claim 41,wherein the anode comprises one or more of the group consisting oflithium metal, lithium-aluminum alloys, lithium-tin alloys, lithiumintercalated carbons, lithium intercalated graphites, calcium metal,aluminum metal, sodium metal, and sodium alloys.
 55. The cell of claim41, wherein the cell further comprises a separator between the anode andthe cathode.
 56. The cell of claim 41, wherein the electrolyte comprisesone or more of the group consisting of liquid electrolytes, gel polymerelectrolytes, and solid polymer electrolytes.
 57. The cell of claim 41,wherein the electrolyte comprises one or more ionic electrolyte salts.58. The cell of claim 57, wherein the one or more ionic electrolytesalts comprises one or more of the group consisting of MCl₄, MAsF₄,MSO₃CF₃, MSO₃CH₃, MBF₄, MB(Ph)₄, MPF₄, MC(SO₂CF₃)₃, MN(SO₂CF₃)₂,

where M is Li or Na.
 59. An electrochemical cell comprising: (a) ananode comprising lithium; (b) a cathode comprising elemental sulfur; and(c) an electrolyte; wherein the apparent density of the cathode is 0.496g/cm³.
 60. The cell of claim 59, wherein the elemental sulfur comprisesparticles, wherein each particle has a diameter of generally less than10 μm.
 61. The cell of claim 59, wherein the thickness of the cathode isabout 25 μm or less.
 62. The cell of claim 59, wherein the thickness ofthe cathode is about 100 μm or less.
 63. The cell of claim 59, whereinthe cell further comprises a separator between the anode and thecathode.
 64. The cell of claim 59, wherein the electrolyte comprises oneor more of the group consisting of liquid electrolytes, gel polymerelectrolytes, and solid polymer electrolytes.
 65. The cell of claim 59,wherein the electrolyte comprises one or more ionic electrolyte salts.66. The cell of claim 65, wherein the one or more ionic electrolytesalts comprises one or more of the group consisting of MCl₄, MAsF₄,MSO₃CF₃, MSO₃CH₃, MBF₄, MB(Ph)₄, MPF₄, MC(SO₂CF₃)₃, MN(SO₂CF₃)₂,

where M is Li or Na.